Varying processes to control transmission characteristics for position determination operations

ABSTRACT

Disclosed are systems, apparatus, devices, methods, media, products, and other implementations, including a method that includes controllably modifying, at a first wireless device, an original unmodified value of at least one PHY-layer signal parameter, such as amplitude, frequency, timestamp, gain, signal equalization, and/or any combination thereof, of a signal according to at least one pre-determined varying signal modification process. The method further includes transmitting to a second wireless device the signal with the controllably modified value of the at least one PHY-layer signal parameter, with the transmitted signal configured to facilitate position determination of the second wireless device when the original unmodified value of the at least one PHY-layer signal parameter is determined at the second wireless device from the controllably modified value of the at least one PHY-layer signal parameter.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present application claims the benefit of and priority to U.S.Provisional Application Ser. No. 61/812,139, entitled “SIGNAL VARIATIONFOR POSITION DETERMINATION PROCESSES,” filed Apr. 15, 2013, and to U.S.Provisional Application Ser. No. 61/891,329, entitled “VARYING PROCESSESTO CONTROL TRANSMISSION CHARACTERISTICS FOR POSITION DETERMINATIONOPERATIONS,” filed Oct. 15, 2013, both of which are assigned to theassignee hereof, and expressly incorporated herein by reference.

BACKGROUND

One technique to facilitate location determination is based on use ofsignal parameters of a signal received at a device whoseposition/location is to be determined. For example, measurements such asround-trip time (RTT), received signal strength indicator (RSSI), etc.,can be used to facilitate position determination through such techniquesas, for example, RTT-fingerprinting, RSSI-fingerprinting, etc.

Signal information needed for position determination (including indoorpositioning determination using signals transmitted by WiFi basestations) can generally be collected by anyone with access to the venue.This may be problematic for venue owners operating thesignal-transmitting base stations, who could lose possible monetizationbenefits they could have received from providing position-determinationservices that are being diverted by 3^(rd) party (e.g., othermapping/location-determination service providers).

Furthermore, future positioning systems will likely leverage on-phonesensor measurements (accelerometers, rate gyros, magnetometers andbarometers) as well as WiFi signals. Beacon messages from APs might beleveraged to obtain position or speed-dependent measurements. Forinstance, the RSSI and the channel impulse response (CIR) as estimatedby a receiver from the beacon messages are dependent on position of thereceiver relative to an AP. Variations in the CIR and the RSSI (i.e.,fast fading statistics) can be used to estimate a mobile's speed (or atthe very least, a stopped state). Currently, it is difficult toprevent/inhibit anyone from leveraging these kinds of receive-onlymeasurements for positioning purposes.

SUMMARY

Disclosed herein are methods, systems, apparatus, devices, products andother implementations, including a method that includes controllablymodifying, at a first wireless device, an original unmodified value ofat least one PRY-layer signal parameter for a signal according to atleast one pre-determined varying signal modification process. The atleast one PHY-layer signal parameter includes, for example, amplitude,frequency, timestamp, gain, signal equalization, and/or any combinationthereof. The method further includes transmitting, to a second wirelessdevice, the signal with a controllably modified value of the at leastone PHY-layer signal parameter, the transmitted signal configured tofacilitate position determination of the second wireless device when theoriginal unmodified value of the at least one PHY-layer signal parameteris determined at the second wireless device from the controllablymodified value of the at least one PHY-layer signal parameter.

Embodiments of the method may include at least some of the featuresdescribed in the present disclosure, including one or more of thefollowing features.

Controllably modifying the original unmodified value of the at least onePHY-layer signal parameter according to the at least one pre-determinedvarying signal modification process may include controllably modifyingoriginal unmodified values of two or more PHY-layer signal parametersaccording to respective different pre-determined varying signalmodification processes.

One of the two or more PHY-layer signal parameters may include at leastone of, for example, delay and/or phase.

Controllably modifying the original unmodified value of the at least onePHY-layer signal parameter according to the at least one pre-determinedvarying signal modification process may include controllably modifyingthe original unmodified value of the at least one PHY-layer signalparameter according to a pseudorandom-time-variation-based process.

Controllably modifying the original unmodified value of the at least onePHY-layer signal parameter according to the at least one pre-determinedvarying signal modification process may include controllably modifyingthe original unmodified value of the at least one PHY-layer signalparameter according to an autoregressive moving average process.

Controllably modifying the original unmodified value of the at least onePHY-layer signal parameter according to the autoregressive movingaverage process may include generating a sequence of random numbersbased on a pseudorandom generator process, inputting the sequence ofrandom numbers to a z-transform implementation of the autoregressivemoving average process to generate a resultant sequence, and modifyingthe original unmodified value of the at least one PHY-layer signalparameter based on the resultant sequence. Respective clocks at thefirst wireless device and the second wireless device may be synchronizedrelative to a reference time, and a second pseudorandom number sequenceat the second wireless device may be generated such that the secondpseudorandom number sequence is synchronized with the sequence of randomnumbers generated at the first wireless device.

The transmitted signal configured to facilitate position determinationat the second wireless device may be configured to facilitate positiondetermination at the second wireless device based on one or more of, forexample, a received signal strength indicator (RSSI)-based positioningdetermination process, a round trip time (RTT)-based positiondetermination process, a speed-based position determination processaided by an inertial navigation system, and/or any combination thereof.

The RSSI-based position determination process may include anRSSI-fingerprinting process (e.g., matching an RSSI signature fromvarious received transmitters to previously collected RSSImeasurements/signatures), and the RTT-based position determinationprocess may include an RTT-fingerprinting process.

The first wireless device comprises may include an access point. Theaccess point may include a WiFi-based station.

The second wireless device may include a preauthorized wireless deviceequipped with an undithering unit configured to enable undithering ofthe signal with the at least one PHY-layer signal parameter valuecontrollably modified at the first wireless device according to the atleast one pre-determined varying signal modification process.

In some variations, a wireless device is disclosed that includes one ormore processors, and storage media including computer instructions. Thecomputer instructions, when executed on the one or more processors,cause operations that include controllably modifying an originalunmodified value of at least one PHY-layer signal parameter for a signalaccording to at least one pre-determined varying signal modificationprocess. The at least one PHY-layer signal parameter includes, forexample, amplitude, frequency, timestamp, gain, signal equalization,and/or any combination thereof. The operations further includetransmitting, to an other wireless device, the signal with acontrollably modified value of the at least one PHY-layer signalparameter, the transmitted signal configured to facilitate positiondetermination of the other wireless device when the original unmodifiedvalue of the at least one PHY-layer signal parameter is determined atthe other wireless device from the controllably modified value of the atleast one PHY-layer signal parameter.

Embodiments of the wireless device may include at least some of thefeatures described in the present disclosure, including at least some ofthe features described above in relation to the method.

In some variations, an apparatus is disclosed. The apparatus includesmeans for controllably modifying an original unmodified value of atleast one PHY-layer signal parameter for a signal according to at leastone pre-determined varying signal modification process. The at least onePHY-layer signal parameter includes, for example, amplitude, frequency,timestamp, gain, signal equalization, and/or any combination thereof.The apparatus further includes means for transmitting, to a receivingwireless device, the signal with a controllably modified value of the atleast one PHY-layer signal parameter, the transmitted signal configuredto facilitate position determination of the receiving wireless devicewhen the original unmodified value of the at least one PHY-layer signalparameter is determined at the receiving wireless device from thecontrollably modified value of the at least one PHY-layer signalparameter.

Embodiments of the apparatus may include at least some of the featuresdescribed in the present disclosure, including at least some of thefeatures described above in relation to the method and the device, aswell as one or more of the following features.

The means for controllably modifying the original unmodified value ofthe at least one PHY-layer signal parameter according to the at leastone pre-determined varying signal modification process may include meansfor controllably modifying original unmodified values of two or morePHY-layer signal parameters according to respective differentpre-determined varying signal modification processes.

The means for controllably modifying the original unmodified value ofthe at least one PHY-layer signal parameter according to the at leastone pre-determined varying signal modification process may include meansfor controllably modifying the original unmodified value of the at leastone PHY-layer signal parameter according to apseudorandom-time-variation-based process.

The means for controllably modifying the original unmodified value ofthe at least one PHY-layer signal parameter according to the at leastone pre-determined varying signal modification process may include meansfor controllably modifying the original unmodified value of the at leastone PHY-layer signal parameter according to an autoregressive movingaverage process.

The means for controllably modifying the original unmodified value ofthe at least one PHY-layer signal parameter according to theautoregressive moving average process may include means for generating asequence of random numbers based on a pseudorandom generator process,means for inputting the sequence of random numbers to a z-transformimplementation of the autoregressive moving average process to generatea resultant sequence, and means for modifying the original unmodifiedvalue of the at least one PHY-layer signal parameter based on theresultant sequence.

In some variations, a processor readable media is disclosed. Theprocessor readable media is programmed with a set of instructionsexecutable on a processor that, when executed, causes operations thatinclude controllably modifying, at a first wireless device, an originalunmodified value of at least one PHY-layer signal parameter for a signalaccording to at least one pre-determined varying signal modificationprocess. The at least one PHY-layer signal parameter includes, forexample, amplitude, frequency, timestamp, gain, signal equalization,and/or any combination thereof. The set of instructions causes furtheroperations including transmitting, to a second wireless device, thesignal with a controllably modified value of the at least one PHY-layersignal parameter, the transmitted signal configured to facilitateposition determination of the second wireless device when the originalunmodified value of the at least one PHY-layer signal parameter isdetermined at the second wireless device from the controllably modifiedvalue of the at least one PHY-layer signal parameter.

Embodiments of the processor-readable media may include at least some ofthe features described in the present disclosure, including at leastsome of the features described above in relation to the method, thedevice, and the apparatus.

In some variations, an additional method is disclosed. The additionalmethod includes receiving, at a first wireless device, a signaltransmitted from a second wireless device, with controllably modified atleast one PHY-layer signal parameter value that was generated accordingto at least one pre-determined varying signal modification processapplied to an original unmodified value of at least one PHY-layer signalparameter. The at least one PHY-layer signal parameter includes, forexample, amplitude, frequency, timestamp, gain, signal equalization, orany combination thereof. The additional method also includesdetermining, from the received signal, original unmodified value of theat least one PHY-layer signal parameter, and determining a position ofthe first wireless device based, at least in part, on the originalunmodified value of the at least one PHY-layer signal parameter of thesignal, determined from the controllably modified at least one PHY-layersignal parameter value of the signal received at the first wirelessdevice.

Embodiments of the additional method may include at least some of thefeatures described in the present disclosure, including at least some ofthe features described above in relation to the first method, thedevice, the apparatus, and the processor-readable media, as well as oneor more of the following features.

The controllably modified at least one PHY-layer signal parameter valueof the received signal generated according to the at least onepre-determined varying signal modification process may includecontrollably modified two or more PHY-layer signal parameter valuesgenerated according to respective different pre-determined varyingsignal modification processes applied to respective original unmodifiedvalues of two or more PHY-layer signal parameters of the signaltransmitted from the second wireless device.

The controllably modified at least one PHY-layer signal parameter valueof the received signal generated according to the at least onepre-determined varying signal modification process may be generatedaccording to a pseudorandom-time-variation-based process applied to theoriginal unmodified value of the at least one PHY-layer signal parameterof the signal transmitted from the second wireless device.

The controllably modified at least one PHY-layer signal parameter valueof the received signal generated according to the at least onepre-determined varying signal modification process may be generatedaccording to an autoregressive moving average process applied to theoriginal unmodified value of the controllably modified at least onePHY-layer signal parameter of the signal transmitted from the secondwireless device.

The controllably modified at least one PHY-layer signal parameter valuegenerated according to the autoregressive moving average process may begenerated by generating, at the second wireless device, a sequence ofrandom numbers based on a pseudorandom generator process, inputting, atthe second wireless device, the sequence of random numbers to az-transform implementation of the autoregressive moving average processto generate a resultant sequence, and modifying, at the second wirelessdevice, the original unmodified value of the at least one PHY-layersignal parameter based on the resultant sequence.

The method may further include synchronizing a first clock at the firstwireless device to a second clock at the second wireless device relativeto a reference time, and generating a second pseudorandom numbersequence at the first wireless device such that the second pseudorandomnumber sequence is synchronized with the sequence of random numbersgenerated at the second wireless device.

Determining the position of the first wireless device may includedetermining the position of the first wireless device based on one ormore of, for example, a received signal strength indicator (RSSI)-basedpositioning determination process, a round trip time (RTT)-basedposition determination process, a speed-based position determinationprocess aided by an inertial navigation system, and/or any combinationthereof.

The RSSI-based position determination process may include anRSSI-fingerprinting process (e.g., matching measured RSSI values to apreviously collected baseline of RSSI measurements/fingerprints), andthe RTT-based position determination process comprises anRTT-fingerprinting process.

The second wireless device may include an access point (e.g., aWiFi-based access point).

The first wireless device may include a preauthorized wireless deviceequipped with an undithering unit configured to enable undithering ofthe signal with the at least one PHY-layer signal parameter valuecontrollably modified at the second wireless device according to the atleast one pre-determined varying signal modification process.

In some variations, an additional wireless device is disclosed. Theadditional wireless device includes one or more processors, and storagemedia. The storage media include computer instructions that, whenexecuted on the one or more processors, cause operations includingreceiving a signal, transmitted from an other wireless device, with acontrollably modified at least one PHY-layer signal parameter value thatwas generated according to at least one pre-determined varying signalmodification process applied to an original unmodified value of at leastone PHY-layer signal parameter. The at least one PHY-layer signalparameter includes, for example, amplitude, frequency, timestamp, gain,signal equalization, and/or any combination thereof. The computerinstructions cause further operations including determining, from thereceived signal, the original unmodified value of the at least onePHY-layer signal parameter, and determining a position of the wirelessdevice based, at least in part, on the original unmodified value of theat least one PHY-layer signal parameter of the signal, determined fromthe controllably modified at least one PHY-layer signal parameter valueof the signal received at the wireless device.

Embodiments of the additional wireless device may include at least someof the features described in the present disclosure, including at leastsome of the features described above in relation to the methods, thefirst device, the apparatus, and the processor-readable media.

In some variations, an additional apparatus is disclosed. The additionalapparatus includes means for receiving a signal, transmitted from atransmitting wireless device, with a controllably modified at least onePHY-layer signal parameter value that was generated according to atleast one pre-determined varying signal modification process applied toan original unmodified value of at least one PHY-layer signal parameter.The at least one PHY-layer signal parameter includes, for example,amplitude, frequency, timestamp, gain, signal equalization, and/or anycombination thereof. The additional apparatus also includes means fordetermining, from the received signal, the original unmodified value ofthe at least one PHY-layer signal parameter, and means for determining aposition of the apparatus based, at least in part, on the originalunmodified value of the at least one PHY-layer signal parameter of thesignal, determined from the controllably modified at least one PHY-layersignal parameter value of the signal received at the apparatus.

Embodiments of the additional apparatus may include at least some of thefeatures described in the present disclosure, including at least some ofthe features described above in relation to the methods, the devices,the first apparatus, and the processor-readable media, as well as one ormore of the following features.

The apparatus may further include means for synchronizing a clock at theapparatus to an other clock at the transmitting wireless device relativeto a reference time, and means for generating a second pseudorandomnumber sequence at the apparatus such that the second pseudorandomnumber sequence is synchronized with the sequence of random numbersgenerated at the transmitting wireless device.

The means for determining the position of the apparatus may includemeans for determining the position of the apparatus based on one or moreof, for example, a received signal strength indicator (RSSI)-basedpositioning determination process, a round trip time (RTT)-basedposition determination process, a speed-based position determinationprocess aided by an inertial navigation system, and/or any combinationthereof.

In some variations, additional processor readable media programmed witha set of instructions executable on a processor is disclosed. The set ofinstructions, when executed, causes operations comprising receiving at afirst wireless device a signal, transmitted from a second wirelessdevice, with a controllably modified at least one PHY-layer signalparameter value that was generated according to at least onepre-determined varying signal modification process applied to anoriginal unmodified value of at least one PHY-layer signal parameter.The at least one PHY-layer signal parameter includes, for example,amplitude, frequency, phase, delay, timestamp, gain, signalequalization, and/or any combination thereof. The set of instructions,when executed, also causes further operations including determining,from the received signal, the original unmodified value of the at leastone PHY-layer signal parameter value, and determining a position of thefirst wireless device based, at least in part, on the originalunmodified value of the at least one PHY-layer signal parameter of thesignal, determined from the controllably modified at least one PHY-layersignal parameter value of the signal received at the first wirelessdevice.

Embodiments of the additional processor readable media may include atleast some of the features described in the present disclosure,including at least some of the features described above in relation tothe methods, the devices, the apparatus, and the firstprocessor-readable media.

In some variations, a further method is disclosed. The further methodincludes determining, at a first wireless device comprising multipletransmit antennas, at least one signal transmission characteristicaccording to at least one pre-determined varying transmissioncharacteristic determination process. The at least one transmissioncharacteristic includes, for example, a transmit antenna selected fromthe multiple transmit antennas, a beam characteristic, a cyclic delaydiversity parameter, and/or any combination thereof. The further methodalso includes transmitting from the first wireless device to a secondwireless device a signal using the at least one signal transmissioncharacteristic determined according to the at least one pre-determinedvarying transmission characteristic determination process. Thetransmitted signal is configured to facilitate position determination ofthe second wireless device upon deriving at the second wireless device areconstructed value of the at least one signal transmissioncharacteristic determined at the first wireless device.

Embodiments of the further method may include at least some of thefeatures described in the present disclosure, including at least some ofthe features described above in relation to the methods, the devices,the apparatus, and the processor-readable media, as well as one or moreof the following features.

The further method may further include controllably modifying anoriginal unmodified value of at least a second signal transmissioncharacteristics according to at least one pre-determined varyingtransmission characteristic modification process, the second signaltransmission characteristic including, for example, signal amplitude,signal frequency, signal timestamp, signal gain, signal equalization,signal delay, signal phase, and/or any combination thereof.

Determining the at least one signal transmission characteristicaccording to the at least one pre-determined varying transmissioncharacteristic determination process may include determining the atleast one signal transmission characteristic according to at least onepseudorandom-time-variation-based process.

Determining the at least one signal transmission characteristicaccording to the at least one pre-determined varying transmissioncharacteristic determination process may include selecting the transmitantenna from the multiple transmit antennas according to apseudorandom-time-variation-based antenna selection process.

Determining the at least one signal transmission characteristicaccording to the at least one pre-determined varying transmissioncharacteristic determination process may include controllably adjusting,according to one or more pseudorandom-time-variation-based beam controlprocesses, a corresponding relative phase and a corresponding amplitudefor each of multiple signals respectively directed to each of themultiple transmit antennas to control a varying beam.

Determining the at least one signal transmission characteristicaccording to the at least one pre-determined varying transmissioncharacteristic determination process may include controllably adjusting,according to at least one pseudorandom-time-variation-based cyclic delayprocess, a corresponding delay added to at least one of multiple signalsrespectively directed to at least one of the multiple transmit antennas.

Determining the at least one signal transmission characteristicaccording to the at least one pre-determined varying transmissioncharacteristic determination process may include determining the atleast one signal transmission characteristic according to at least oneautoregressive moving average process.

Determining the at least one signal transmission characteristicaccording to the at least one autoregressive moving average process mayinclude generating a sequence of random numbers based on a pseudorandomgenerator process, inputting the sequence of random numbers to az-transform implementation of the at least one autoregressive movingaverage process to generate a resultant sequence, and determining the atleast one signal transmission characteristic based on the resultantsequence.

Respective clocks at the first and second wireless devices may besynchronized relative to a reference time, and a second pseudorandomnumber sequence at the second wireless device may be generated such thatthe second pseudorandom number sequence is synchronized with thesequence of random numbers generated at the first wireless device.

The transmitted signal configured to facilitate position determinationof the second wireless device may be configured to facilitate positiondetermination of the second wireless device based on one or more of, forexample, a received signal strength indicator (RSSI)-based positioningdetermination process, a round trip time (RTT)-based positiondetermination process, a speed-based position determination processaided by an inertial navigation system, and/or any combination thereof.

The first wireless device may include an access point.

The second wireless device may include a preauthorized wireless deviceequipped with an undithering unit configured to enable undithering ofthe signal transmitted from the first wireless device using the at leastone signal transmission characteristic determined according to the atleast one pre-determined varying transmission characteristicdetermination process.

In some variations, a further wireless device is disclosed. The furtherwireless device includes multiple transmit antennas, one or moreprocessors, and storage media comprising computer instructions. Thecomputer instructions, when executed on the one or more processors,cause operations that include determining, at the wireless device, atleast one signal transmission characteristic according to at least onepre-determined varying transmission characteristic determinationprocess. The at least one transmission characteristic includes, forexample, a transmit antenna selected from the multiple transmitantennas, a beam characteristic, a cyclic delay diversity parameter,and/or any combination thereof. The computer instructions also causeoperations including transmitting from the wireless device to an otherwireless device a signal using the at least one signal transmissioncharacteristic determined according to the at least one pre-determinedvarying transmission characteristic determination process. Thetransmitted signal is configured to facilitate position determination ofthe other wireless device upon deriving at the other wireless device areconstructed value of the at least one signal transmissioncharacteristic determined at the wireless device.

Embodiments of the further wireless device may include at least some ofthe features described in the present disclosure, including at leastsome of the features described above in relation to the methods, thedevices, the apparatus, and the processor-readable media.

In some variations, a further apparatus is disclosed. The furtherapparatus includes means for determining at least one signaltransmission characteristic according to at least one pre-determinedvarying transmission characteristic determination process. The at leastone transmission characteristic includes one or more of, for example, atransmit antenna selected from multiple transmit antennas, a beamcharacteristic, a cyclic delay diversity parameter, and/or anycombination thereof. The further apparatus also includes means fortransmitting to a receiving wireless device a signal using the at leastone signal transmission characteristic determined according to the atleast one pre-determined varying transmission characteristicdetermination process. The transmitted signal is configured tofacilitate position determination of the receiving wireless device uponderiving at the receiving wireless device a reconstructed value of theat least one signal transmission characteristic determined at theapparatus.

Embodiments of the further apparatus may include at least some of thefeatures described in the present disclosure, including at least some ofthe features described above in relation to the methods, the devices,the apparatus, and the processor-readable media, as well as one or moreof the following features.

The further apparatus may additionally include means for controllablymodifying an original unmodified value of at least a second signaltransmission characteristics according to at least one pre-determinedvarying transmission characteristic modification process, the secondsignal transmission characteristic including, for example, signalamplitude, signal frequency, signal timestamp, signal gain, signalequalization, signal delay, signal phase, and/or any combinationthereof.

The means for determining the at least one signal transmissioncharacteristic according to the at least one pre-determined varyingtransmission characteristic determination process may include means forselecting the transmit antenna from the multiple transmit antennasaccording to a pseudorandom-time-variation-based antenna selectionprocess.

The means for determining the at least one signal transmissioncharacteristic according to the at least one pre-determined varyingtransmission characteristic determination process may include means forcontrollably adjusting, according to one or morepseudorandom-time-variation-based beam control processes, acorresponding relative phase and a corresponding amplitude for each ofmultiple signals respectively directed to each of the multiple transmitantennas to control a varying beam.

The means for determining the at least one signal transmissioncharacteristic according to the at least one pre-determined varyingtransmission characteristic determination process may include means forcontrollably adjusting, according to at least onepseudorandom-time-variation-based cyclic delay process, a correspondingdelay added to at least one of multiple signals respectively directed toat least one of the multiple transmit antennas.

The means for determining the at least one signal transmissioncharacteristic according to the at least one pre-determined varyingtransmission characteristic determination process may include means fordetermining the at least one signal transmission characteristicaccording to at least one autoregressive moving average process.

The means for determining the at least one signal transmissioncharacteristic according to the at least one autoregressive movingaverage process may include means for generating a sequence of randomnumbers based on a pseudorandom generator process, means for inputtingthe sequence of random numbers to a z-transform implementation of the atleast one autoregressive moving average process to generate a resultantsequence, and means for determining the at least one signal transmissioncharacteristic based on the resultant sequence.

In some variations, further processor readable media is provided. Thefurther processor readable media is programmed with a set ofinstructions executable on a processor that, when executed, causesoperations including determining, at a first wireless device comprisingmultiple antennas, at least one signal transmission characteristicaccording to at least one pre-determined varying transmissioncharacteristic determination process. The at least one transmissioncharacteristic includes, for example, a transmit antenna selected fromthe multiple transmit antennas, a beam characteristic, a cyclic delaydiversity parameter, and/or any combination thereof. The set ofinstructions, when executed, also causes the operations of transmittingfrom the first wireless device to a second wireless device a signalusing the at least one signal transmission characteristic determinedaccording to the at least one pre-determined varying transmissioncharacteristic determination process. The transmitted signal isconfigured to facilitate position determination of the second wirelessdevice upon deriving at the second wireless device a reconstructed valueof the at least one signal transmission characteristic determined at thefirst wireless device.

Embodiments of the further processor readable media may include at leastsome of the features described in the present disclosure, including atleast some of the features described above in relation to the methods,the devices, the apparatus, and the processor-readable media.

In some variations, an additional method is provided that includesreceiving, at a first wireless device, a signal transmitted from asecond wireless device with multiple transmit antennas using at leastone signal transmission characteristic initially determined at the otherwireless device according to at least one pre-determined varyingtransmission characteristic determination process. The at least onesignal transmission characteristic includes, for example, a transmitantenna selected from the multiple transmit antennas, a beamcharacteristic, a cyclic delay diversity parameter, and/or anycombination thereof. The additional method also includes deriving, atthe first wireless device, a reconstructed value of the at least onesignal transmission characteristic initially determined at the secondwireless device, and determining a position of the first wireless devicebased, at least in part, on the derived reconstructed value of the atleast one signal transmission characteristic initially determined at thesecond wireless device according to the at least one pre-determinedvarying transmission characteristic determination process.

Embodiments of the additional method may include at least some of thefeatures described in the present disclosure, including at least some ofthe features described above in relation to the methods, the devices,the apparatus, and the processor-readable media, as well as one or moreof the following features.

The additional method may further include determining, from the receivedsignal, an original unmodified value of at least a second signaltransmission characteristic controllably modified at the second wirelessdevice according to at least one pre-determined varying transmissioncharacteristic modification process, the at least second signaltransmission characteristic including, for example, signal amplitude,signal frequency, signal timestamp, signal gain, signal equalization,signal delay, signal phase, and/or any combination thereof.

The at least one signal transmission characteristic, initiallydetermined according to the at least one pre-determined varyingtransmission characteristic determination process, may be initiallydetermined at the second wireless device according to at least onepseudorandom-time-variation-based process.

The at least one signal transmission characteristic, initiallydetermined according to the at least one pre-determined varyingtransmission characteristic determination process, may be initiallydetermined at the second wireless device according to at least oneautoregressive moving average process.

The at least one signal transmission characteristic initially determinedaccording to the at least one pre-determined varying transmissioncharacteristic determination process may include the transmit antennaselected at the second wireless device from the multiple transmitantennas according to a pseudorandom-time-variation-based antennaselection process.

The at least one signal transmission characteristic determined accordingto the at least one pre-determined varying transmission characteristicdetermination process may include a corresponding relative phase and acorresponding amplitude for each of multiple signals, respectivelydirected to each of the multiple transmit antennas to control a varyingbeam, the corresponding relative phase and the corresponding amplitudefor the each of the multiple signals being controllably adjusted at thesecond wireless device according to one or morepseudorandom-time-variation-based beam forming processes.

The at least one signal transmission characteristic initially determinedaccording to the at least one pre-determined varying transmissioncharacteristic determination process may include a corresponding delayadded to at least one of multiple signals, respectively directed to atleast one of the multiple transmit antennas, controllably adjusted atthe second wireless device according to a respective at least onepseudorandom-time-variation-based cyclic delay process.

The first wireless device may include a preauthorized wireless deviceequipped with an undithering unit configured to enable undithering ofthe signal transmitted from the second wireless device using the atleast one signal transmission characteristic determined according to theat least one pre-determined varying transmission characteristicdetermination process.

In some variations, an additional wireless device is disclosed. Theadditional wireless device includes one or more processors, and storagemedia comprising computer instructions. The computer instructions, whenexecuted on the one or more processors, cause operations includingreceiving at the wireless device a signal transmitted from an otherwireless device with multiple transmit antennas using at least onesignal transmission characteristic initially determined at the otherwireless device according to at least one pre-determined varyingtransmission characteristic determination process, with the at least onesignal transmission characteristic including, for example, a transmitantenna selected from the multiple transmit antennas, a beamcharacteristic, a cyclic delay diversity parameter, and/or anycombination thereof. The computer instructions, when executed, alsocause operations including deriving, at the wireless device, areconstructed value of the at least one signal transmissioncharacteristic initially determined at the other wireless device, anddetermining a position of the wireless device based, at least in part,on the derived reconstructed value of the at least one signaltransmission characteristic initially determined at the other wirelessdevice according to the at least one pre-determined varying transmissioncharacteristic determination process.

Embodiments of the additional wireless device may include at least someof the features described in the present disclosure, including at leastsome of the features described above in relation to the methods, thedevices, the apparatus, and the processor-readable media.

In some variations, an additional apparatus is disclosed. The additionalapparatus includes means for receiving a signal transmitted from atransmitting wireless device with multiple transmit antennas using atleast one signal transmission characteristic initially determined at thetransmitting wireless device according to at least one pre-determinedvarying transmission characteristic determination process. The at leastone signal transmission characteristic includes, for example, a transmitantenna selected from the multiple transmit antennas, a beamcharacteristic, a cyclic delay diversity parameter, and/or anycombination thereof. The additional apparatus also includes means forderiving a reconstructed value of the at least one signal transmissioncharacteristic initially determined at the transmitting wireless device,and means for determining a position of the apparatus based, at least inpart, on the derived reconstructed value of the at least one signaltransmission characteristic initially determined at the transmittingwireless device according to the at least one pre-determined varyingtransmission characteristic determination process.

Embodiments of the additional apparatus may include at least some of thefeatures described in the present disclosure, including at least some ofthe features described above in relation to the methods, the devices,the apparatus, and the processor-readable media, as well as thefollowing feature.

The additional apparatus may further include means for determining, fromthe received signal, an original unmodified value of at least a secondsignal transmission characteristics controllably modified at thetransmitting wireless device according to at least one pre-determinedvarying transmission characteristic modification process, with the atleast second signal transmission characteristic including, for example,signal amplitude, signal frequency, signal timestamp, signal gain,signal equalization, signal delay, signal phase, and/or any combinationthereof.

In some variations, an additional processor readable media is provided.The additional processor readable media is programmed with a set ofinstructions executable on a processor that, when executed, causesoperations including receiving at a first wireless device a signaltransmitted from a second wireless device with multiple transmitantennas using at least one signal transmission characteristic initiallydetermined at the second wireless device according to at least onepre-determined varying transmission characteristic determinationprocess. The at least one signal transmission characteristic includes,for example, a transmit antenna selected from the multiple transmitantennas, a beam characteristic, a cyclic delay diversity parameter,and/or any combination thereof. The set of instructions also causesoperations including deriving, at the first wireless device, areconstructed value of the at least one signal transmissioncharacteristic initially determined at the second wireless device, anddetermining a position of the first wireless device based, at least inpart, on the derived reconstructed value of the at least one signaltransmission characteristic initially determined at the second wirelessdevice according to the at least one pre-determined varying transmissioncharacteristic determination process.

Embodiments of the additional processor readable media may include atleast some of the features described in the present disclosure,including at least some of the features described above in relation tothe methods, the devices, the apparatus, and the processor-readablemedia.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly or conventionally understood. As usedherein, the articles “a” and “an” refer to one or to more than one(i.e., to at least one) of the grammatical object of the article. By wayof example, “an element” means one element or more than one element.“About” and/or “approximately” as used herein when referring to ameasurable value such as an amount, a temporal duration, and the like,encompasses variations of ±20% or ±10%, ±5%, or +0.1% from the specifiedvalue, as such variations are appropriate to in the context of thesystems, devices, circuits, methods, and other implementations describedherein. “Substantially” as used herein when referring to a measurablevalue such as an amount, a temporal duration, a physical attribute (suchas frequency), and the like, also encompasses variations of ±20% or±10%, ±5%, or +0.1% from the specified value, as such variations areappropriate to in the context of the systems, devices, circuits,methods, and other implementations described herein.

As used herein, including in the claims, “or” or “and” as used in a listof items prefaced by “at least one of” or “one or more of” indicatesthat any combination of the listed items may be used. For example, alist of “at least one of A, B, or C” includes any of the combinations Aor B or C or AB or AC or BC and/or ABC (i.e., A and B and C).Furthermore, to the extent more than one occurrence or use of the itemsA, B, or C is possible, multiple uses of A, B, and/or C may form part ofthe contemplated combinations. For example, a list of “at least one ofA, B, or C” may also include AA, AAB, AAA, BB, etc.

As used herein, including in the claims, unless otherwise stated, astatement that a function, operation, or feature, is “based on” an itemand/or condition means that the function, operation, function is basedon the stated item and/or condition and may be based on one or moreitems and/or conditions in addition to the stated item and/or condition.

Other and further objects, features, aspects, and advantages of thepresent disclosure will become better understood with the followingdetailed description of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of an example operating environment inwhich a mobile device may operate.

FIG. 2 is a schematic diagram of an example mobile device.

FIG. 3 is a schematic diagram of an example access point.

FIG. 4 is a flowchart of an example signal-modification procedure.

FIG. 5 is a flowchart of an example procedure to perform locationdetermination using dithered signals.

FIG. 6 is a flowchart of an example procedure to control/determinetransmission characteristics.

FIG. 7 is a flowchart of another example procedure to perform locationdetermination using dithered signals

FIG. 8 is a schematic diagram of an example computing system.

Like reference symbols in the various drawings indicate like elements.

DESCRIPTION

Disclosed herein are systems, apparatus, devices, products, media,methods, and other implementations to, among other things, limit, oreven prevent/inhibit, position determination processes (and alsoinhibit/prevent fingerprinting collection processes in order to inhibitposition determination based on previously collected RSSI or RTTfingerprints) performed by third parties. In some embodiments, theimplementations described herein limit/inhibit position determinationfunctionality by unauthorized parties without affecting/impacting WiFiconnectivity service, and without limiting or interfering with positiondetermination functionality by authorized parties, nor harming thepositioning service for authorized users, applications, and/or devices.Additionally, in some embodiments, the implementations described hereindo not change the content included in or represented by the unprocessedor processed signals, nor do they interfere with the communication ofthe content represented by the signals being modified.

The implementations described herein generally provide more flexibilityover implementations that include position determination applicationsthat can be controlled on the mobile devices on which they areinstalled. For example, a service that is implemented in a High-levelOperating System (HLOS), such as, for example, iOS, Android, WindowsPhone, etc., may provide a position of different qualities for twolocation-based services (LBS) applications that use the same service,but with one LBS including authorization of the venue owner, and theother one without. Because signal measurables are varied (or dithered)at a low network layer level (e.g., the PHY layer), unauthorized users,unauthorized positioning applications, and/or unauthorized devices willreceive dithered signals (and thus dithered measurements) and will thusonly be able to produce low-quality position estimates. On the otherhand, authorized users, authorized applications, and/or authorizeddevices will be able to remove the dithering and generate high-qualityposition estimates. For example, in some implementations, authorizeddevices may be equipped with specific integrated circuits/modulesconfigured to dither signals to be transmitted and/or undither receivedsignals in the manner described herein. In such implementations, AP'swith dithering/undithering units (realized as, for example, anintegrated circuit, firmware, a hardware or software-based driver, etc.)work transparently with dithering/undithering WiFi hardware. Thus, WiFidithering/undithering units (in authorized devices) would be configured“out of the box” to handle/process proprietary dithering. For instance,the dithering/undithering-equipped AP's could transmit the unditheringparameters in an encrypted, vendor-specific data field in beaconpackets. Alternatively and/or additionally, dithering/undithering unitsmay be configured to undither received communications (and/or ditheroutgoing communications) according to pre-determineddithering/undithering functions. In contrast, mobile devices without theproper dithering/undithering WiFi units would not be able to unditherdithered communications from other devices. Those unauthorized deviceswould therefore have to rely on authorized applications (or licensedHLOS drivers, etc.) configured to reverse the PHY dithering employed bytransmitting devices.

As will be described in greater details below, in some embodiments, RSSIfingerprinting position determination procedures and/or time-basedfingerprinting position determination procedures may beprevented/inhibited. Fingerprinting processes are based on the conceptof matching RSSI and/or RTT measurements to previously obtainedfingerprinting measurements that are associated with particularpositions. For example, RSSI fingerprinting measurements taken at aparticular location (corresponding to signal parameters received fromone or more base stations) will match previously obtained measurements,with generally only noise and slight changes in RF propagationconditions accounting for the difference of readings. The situation issimilar for RTT-fingerprinting-based processes, but with the round-triptime being the measurement that is assumed substantially invariantbetween the initial fingerprinting profile collection measurements(i.e., to establish a baseline of measurements acquired from differentpositions) and subsequent RTT measurement operations. In someembodiments, fingerprinting operations to establish a baseline offingerprints occur prior to, and often independently of, positiondetermination. Generally, the RSSI- and/or RTT-fingerprints arecollected in a deliberate survey campaign. Alternatively and/oradditionally, the fingerprint database can be built up over time viacrowdsourcing. Typically, the compact/summarized version of thefingerprint database (e.g. RSSI/RTT heat maps) is sent to the mobile forreal-time use in a positioning engine. In some embodiments,fingerprinting measurements (to establish a baseline of measurements)are initially obtained and are associated with known locations of themeasuring device. Subsequently, at later time points, RTT and/or RSSImeasurements may be taken (by the same or different measuring device)that are compared to the baseline measurements to enable determining themeasuring device's actual or approximate position. In some embodiments,multilateration-based position determination procedures based, forexample, on RTT data, RSSI plus a path loss model, etc., may also beprevented/inhibited by employing one or more of the signal modificationprocedures described herein.

In some embodiments, to inhibit position determination functionality(and/or operations to collect a baseline of fingerprints) by, forexample, unauthorized parties, transmission characteristics, such assignal parameters (e.g., PHY-layer signal parameters such as amplitude,frequency, etc.) are modified at an access point in some pre-determinedvarying manner, e.g., the value or amount that is used to modify thesignal may be varied as a function of time, position, etc. For example,at least one PHY-layer signal parameter (which may also be referred toherein as a transmission characteristic) may be varied according to apseudorandom time varying signal modification process that is known tothe transmitting and to the receiving devices. In some embodiments, morethan one signal parameter may be controllably modified, with eachparameter being modified according to a different pre-determined varyingsignal modification process. At least one of the two or more PHY-layerparameters may include, in some embodiments, phase and/or delay. Thesignals with the at least one modified parameter value can bereconstructed, and/or synchronized, by the receiving device to thusdetermine the original/initial value (i.e., prior to being modified atthe transmitting end in accordance with some varying signal modificationprocess(s)) of the at least one signal parameter of the signaltransmitted by the transmitting wireless device (such as an accesspoint).

In some embodiments, each transmitting wireless device (e.g., AP) mayuse its own unique varying signal modification process, such as its ownunique pseudorandom time varying signal modification process. Generally,a common and synchronized time variation across all transmitting devices(e.g., transmitting AP's) may not be effective to inhibit positiondetermination by unauthorized parties because the common varying signalmodification process would then become a common mode error, and couldthus be eliminated.

In some embodiments, perturbation to the signal parameters may be of aconstant offset value, or a continuously varying value, that may givethe appearance of “natural” noise on the measurements (e.g., due toenvironmental conditions, such as temperature), or may include acontinuously varying value added to a constant offset (e.g., a DCvalue). In some embodiments, the pre-determined varying signalmodification processes (also referred to as dithering) applied to thevarious signal parameters of the transmitted signals may includeprocesses such as, for example, an autoregressive moving average (ARMA)process. A random seed can be communicated to the positioning device(s),possibly in an encrypted manner, to be used as a dithering correctionkey (e.g., authorized devices, such as mobile devices equipped withdithering/undithering units, such as a dithering/undithering chip,firmware and/or driver, may be configured to decrypt such encryptedcommunications sent from AP's equipped with dithering/undithering unitsto thus obtain the seed). The amplitude, timing, other signalparameters, and varying signal modification processes used may becoordinated from a controller of a managed WiFi network.

In some embodiments, the variations to the values of the signalparameters being modified should be sufficiently large to overwhelmnative errors of the positioning engines, but small enough so as not toimpact connectivity of the receiving wireless devices to thetransmitting wireless devices. In some embodiments, 10 dB of totalexcursion may be used. For instance, in the case of AP transmit power(Tx), the pseudo-random variation can be up to 10 dB without perturbingnormal connectivity.

Thus, disclosed herein are methods, devices, systems, apparatus,products, and other implementations, including a method that includescontrollably modifying at a first wireless device (e.g., a terrestrialaccess point) an original (initial) unmodified value of at least onePHY-layer signal parameter for a signal according to at least onepre-determined varying signal modification process, and transmitting toa second wireless device (e.g., a mobile phone) the signal with thecontrollably modified value of the at least one PHY-layer signalparameter. The at least one PHY-layer signal parameter includes, forexample, amplitude, frequency, timestamp, gain, signal equalization,and/or any combination thereof. The transmitted signal is configured tofacilitate position determination of the second wireless device (e.g.,based on fingerprinting procedures, signal timing procedures, signalstrength procedures, etc.) when the original unmodified value of the atleast one PHY-layer signal parameter is determined at the secondwireless device from the controllably modified value of the at least onePHY-layer signal parameter. In some embodiments, the at least onePHY-layer signal parameter may include one or more of, for example,amplitude, signal equalization (e.g., for OFDM modulated signals),frequency, phase, and/or delay (or any combination thereof).

In some embodiments, another type of dithering process may be used withsuch systems as, for example, multiple input and multiple output (MIMO)systems (e.g., multiple antennas at transmit and/or receive ends).Particularly, in some embodiments, successive beacons packets can betransmitted on different antennas selected based on, for example, apseudorandom selection process that may be known only to thetransmitting device and to authorized users, applications, and/ordevices. Performing such variable antenna selection procedure may becombined with dithering processes performed with respect to PHY-layersignal parameters (as described herein). Use of variable antennaselection process may render positioning and fingerprinting procedureswith dithered signals more difficult for unauthorized users,applications, and/or devices to overcome.

In some implementations, a Cyclic Delay Diversity parameter could bedithered in a pseudo-random fashion over time. For unauthorizedapplications and users, the net effect would be a time-varying channelfrequency response (CFR), even when the receiver and transmitter are notmoving relative to each other (e.g., the mobile device is stationary).Such a modification process may be combined, in some embodiments, withPHY-layer signal parameter dithering to make it more difficult forunauthorized users, applications, and/or to use CFR-based processes,such as CFR fingerprinting and CFR-based range and range rate (e.g.,speed) estimation. Additionally, for unicast messages, antenna beamattributes (e.g., to control beam steering and/or forming) could also bedithered. For instance, the angle (azimuth and elevation) of the antennabeam pattern maximum as well as the overall beam pattern could bedithered by modifying the relative phase and amplitude of the signalsdirected to each antenna. This would help to inhibit/preventunauthorized positioning and fingerprinting operations that leverageangle of arrival (AOA) measurements and CFR measurements. Here too, beamattribute dithering could be combined with the other PHY-layer signalparameter dithering procedures, as described herein.

Thus, in some embodiments, a method is provided which includesdetermining, at a first wireless device comprising multiple transmitantennas, at least one signal transmission characteristic according toat least one pre-determined varying transmission characteristicdetermination process. The at least one transmission characteristicincludes, for example, a transmit antenna selected from the multipletransmit antennas, a beam characteristic, a cyclic delay diversityparameter, and/or any combination thereof. The method further includestransmitting from the first wireless device to a second wireless devicea signal using the at least one signal transmission characteristicdetermined according to the at least one pre-determined varyingtransmission characteristic determination process. By deriving at thesecond wireless device a reconstructed value of the transmissioncharacteristic determined at the first wireless device, the receivingwireless device can obtain location determination information that wouldotherwise be skewed if the receiving device did not have knowledge ofthe varying process applied to the at least one transmissioncharacteristic at the transmitting device.

With reference to FIG. 1, shown is a schematic diagram of an exampleoperating environment 100 in which a mobile device 108 operates, e.g., amobile device configured to perform location determination facilitated,in part, by signals received from one or more transmitting wirelessdevices (e.g., terrestrial access points), where the received signalsinclude at least one signal parameter (e.g., physical-layer, orPHY-layer, parameters, such as amplitude, frequency, etc.) that has beencontrollably modified using at least one pre-determined varying signalmodification process. The mobile device (also referred to as a wirelessdevice or as a mobile station) 108 may be configured, in someembodiments, to operate and interact with multiple types of othercommunication systems/devices, including local area network devices (ornodes), such as WLAN for indoor communication, femtocells, Bluetooth®wireless technology-based transceivers, and other types of indoorcommunication network nodes, wide area wireless network nodes, satellitecommunication systems, etc., and as such the mobile device 108 mayinclude one or more interfaces to communicate with the various types ofcommunications systems. As used herein, communicationsystems/devices/nodes with which the mobile device 108 may communicateare also referred to as access points (AP's).

As noted, the environment 100 may contain one or more different types ofwireless communication systems or nodes. Such nodes, also referred to aswireless access points (or WAPs) may include LAN and/or WAN wirelesstransceivers, including, for example, WiFi base stations, femto celltransceivers, Bluetooth® wireless technology transceivers, cellular basestations, WiMax transceivers, etc. Thus, for example, and with continuedreference to FIG. 1, the environment 100 may include Local Area NetworkWireless Access Points (LAN-WAPs) 106 a-e that may be used for wirelessvoice and/or data communication with the mobile device 108. The LAN-WAPs106 a-e may also be utilized, in some embodiments, as independentssources of position data, e.g., through fingerprinting-based procedures,through implementation of multilateration-based procedures based, forexample, on timing-based techniques (e.g., RTT-based techniques, etc.The LAN-WAPs 106 a-e can be part of a Wireless Local Area Network(WLAN), which may operate in buildings and perform communications oversmaller geographic regions than a WWAN. Additionally in someembodiments, the LAN-WAPs 106 a-e could also be pico or femto cells. Insome embodiments, the LAN-WAPs 106 a-e may be part of, for example, WiFinetworks (802.11x), cellular piconets and/or femtocells, Bluetooth®wireless technology Networks, etc. The LAN-WAPs 106 a-e can also includea Qualcomm indoor positioning system (QUIPS). A QUIPS implementationmay, in some embodiments, be configured so that a mobile device cancommunicate with a server that provides the device with data (such as toprovide the assistance data, e.g., floor plans, AP MAC IDs, RSSI maps,etc.) for a particular floor or some other region where the mobiledevice is located. Although five (5) LAN-WAP access points are depictedin FIG. 1, any number of such LAN-WAP's may be used, and, in someembodiments, the environment 100 may include no LAN-WAPs access pointsat all, or may include a single LAN-WAP access point.

One or more of the LAN-WAP nodes depicted in FIG. 1 may be configured tocontrollably modify an original unmodified value of at least onePHY-layer parameters of the signals that it is to transmit in order toprevent or inhibit those transmitted signals from being used forposition determination by unauthorized users. Because an unauthorizeddevice would not have information on the process(es) that need to beapplied to reverse the signal modification process performed by thetransmitting device (in order to determine the original value of thePHY-layer parameter before it was modified by a pre-determined varyingsignal modification process), the unauthorized receiving device willtherefore have incorrect/skewed PHY-layer parameter values, thus makingit difficult (or altogether preventing) the derivation of an estimateddevice position based on signals received from the transmittingdevice(s). Although PHY-layer parameters are controllably modified bythe transmitting device, the modification process does not necessarilymodify the data content represented by the signal (e.g., themodification process does not necessarily modify digital/packetinformation carried/represented by the signals whose PHY-layerparameters were controllably modified). In some embodiments, one or moreof the LAN-WAP nodes may also be configured to inhibit locationdetermination functionality (e.g., at a receiving device such as themobile device 108 or any of the WAP nodes) by applying at least onevarying process to, for example, an antenna-based transmissioncharacteristic.

As further shown in FIG. 1, the environment 100 may also include aplurality of one or more types of Wide Area Network Wireless AccessPoints (WAN-WAPs) 104 a-c, which may be used for wireless voice and/ordata communication, and may also serve as another source of independentinformation through which the mobile device 108 may determine itsposition/location. In some embodiments, one or more of the WAN-WAPs 104a-c may also be configured to controllably modify the value of at leastone PHY-layer parameters of the signals that it is to transmit (and/orcontrol the value of, for example, transmission characteristics such asantenna-based transmission characteristics) in order to prevent orinhibit those transmitted signals from being used for positiondetermination by unauthorized users, and to transmit these signals withthe controllably modified at least one PHY-layer parameter value (and/ortransmit the signal using the controllably adjusted value of the atleast one transmission characteristic, e.g., antenna-based transmissioncharacteristic).

The WAN-WAPs 104 a-c may be part of wide area wireless network (WWAN),which may include cellular base stations, and/or other wide areawireless systems, such as, for example, WiMAX (e.g., 802.16). A WWAN mayinclude other known network components which are not shown in FIG. 1.Typically, each WAN-WAPs 104 a-104 c within the WWAN may operate fromfixed positions or may be moveable nodes, and may provide networkcoverage over large metropolitan and/or regional areas. Although three(3) WAN-WAPs are depicted in FIG. 1, any number of such WAN-WAPs may beused. In some embodiments, the environment 100 may include no WAN-WAPsat all, or may include a single WAN-WAP.

Communication to and from the mobile device 108 (to exchange data,enable position determination of the device 108, etc.) may beimplemented, in some embodiments, using various wireless communicationnetworks such as a wide area wireless network (WWAN), a wireless localarea network (WLAN), a wireless personal area network (WPAN), and so on.The term “network” and “system” may be used interchangeably. A WWAN maybe a Code Division Multiple Access (CDMA) network, a Time DivisionMultiple Access (TDMA) network, a Frequency Division Multiple Access(FDMA) network, an Orthogonal Frequency Division Multiple Access (OFDMA)network, a Single-Carrier Frequency Division Multiple Access (SC-FDMA)network, a WiMax (IEEE 802.16), and so on. A CDMA network may implementone or more radio access technologies (RATs) such as cdma2000,Wideband-CDMA (W-CDMA), and so on. Cdma2000 includes IS-95, IS-2000,and/or IS-856 standards. A TDMA network may implement Global System forMobile Communications (GSM), Digital Advanced Mobile Phone System(D-AMPS), or some other RAT. GSM and W-CDMA are described in documentsfrom a consortium named “3rd Generation Partnership Project” (3GPP).Cdma2000 is described in documents from a consortium named “3rdGeneration Partnership Project 2” (3GPP2). 3GPP and 3GPP2 documents arepublicly available. A WLAN may also be implemented, at least in part,using an IEEE 802.11x network, and a WPAN may be a Bluetooth® wirelesstechnology network, an IEEE 802.15x, or some other type of network. Thetechniques described herein may also be used for any combination ofWWAN, WLAN and/or WPAN.

In some embodiments, and as further depicted in FIG. 1, the mobiledevice 108 may also be configured to at least receive information from aSatellite Positioning System (SPS) 102 a-b, which may be used as anindependent source of position information for the mobile device 108.The mobile device 108 may thus include one or more dedicated SPSreceivers specifically designed to receive signals for derivinggeo-location information from the SPS satellites. Thus, in someembodiments, the mobile device 108 may communicate with any one or acombination of the SPS satellites 102 a-b, the WAN-WAPs 104 a-c, and/orthe LAN-WAPs 106 a-e. In some embodiments, each of the aforementionedsystems can provide an independent information estimate of the positionfor the mobile device 108 using different techniques. In someembodiments, the mobile device may combine the solutions derived fromeach of the different types of access points to improve the accuracy ofthe position data. It is also possible to hybridize measurements fromdifferent systems to get a position estimate, particularly when there isan insufficient number of measurements from all individual systems toderive a position. For instance, in an urban canyon setting, only oneGNSS satellite may be visible and provide decent measurements (i.e. rawpseudorange and Doppler observables). By itself, this single measurementcannot provide a position solution. However, it could be combined withmeasurements from urban WiFi APs, or WWAN cell ranges. When deriving aposition using the access points 104 a-b, 106 a-e, and/or the satellites102 a-b, at least some of the operations/processing may be performedusing a positioning server 110 which may be accessed, in someembodiments, via a network 112.

In embodiments in which the mobile device 108 can receive satellitesignals, the mobile device may utilize a receiver (e.g., a GNSSreceiver) specifically implemented for use with the SPS to extractposition data from a plurality of signals transmitted by SPS satellites102 a-b. Transmitted satellite signals may include, for example, signalsmarked with a repeating pseudo-random noise (PN) code of a set number ofchips and may be located on ground based control stations, userequipment and/or space vehicles. The techniques provided herein may beapplied to or otherwise enabled for use in various other systems, suchas, e.g., Global Positioning System (GPS), Galileo, Glonass, Compass,Quasi-Zenith Satellite System (QZSS) over Japan, Indian RegionalNavigational Satellite System (IRNSS) over India, Beidou over China,etc., and/or various augmentation systems (e.g., a Satellite BasedAugmentation System (SBAS)) that may be associated with or otherwiseenabled for use with one or more global and/or regional navigationsatellite systems. By way of example but not limitation, an SBAS mayinclude an augmentation system(s) that provides integrity information,differential corrections, etc., such as, e.g., Wide Area AugmentationSystem (WAAS), European Geostationary Navigation Overlay Service(EGNOS), Multi-functional Satellite Augmentation System (MSAS), GPSAided Geo Augmented Navigation or GPS and Geo Augmented Navigationsystem (GAGAN), and/or the like. Thus, as used herein an SPS may includeany combination of one or more global and/or regional navigationsatellite systems and/or augmentation systems, and SPS signals mayinclude SPS, SPS-like, and/or other signals associated with such one ormore SPS.

As used herein, a mobile device or station (MS) refers to a device suchas a cellular or other wireless communication device, personalcommunication system (PCS) device, personal navigation device (PND),Personal Information Manager (PIM), Personal Digital Assistant (PDA), atablet device, a laptop, recreational navigational-capable sportingdevices (e.g., a jogging/cycling equipped with a GPS and/or WiFIreceiver), or some other suitable mobile device which may be capable ofreceiving wireless communication and/or navigation signals, such asnavigation positioning signals. The term “mobile station” (or “mobiledevice”) is also intended to include devices which communicate with apersonal navigation device (PND), such as by short-range wireless (e.g.,Bluetooth® wireless technology), infrared, wireline connection, or otherconnection, regardless of whether satellite signal reception, assistancedata reception, and/or position-related processing occurs at the deviceor at the PND. Also, “mobile station” is intended to include alldevices, including wireless communication devices, computers, laptops,tablet, etc., which are capable of communication with a server, such asvia the Internet, WiFi, or other network, regardless of whethersatellite signal reception, assistance data reception, and/orposition-related processing occurs at the device, at a server, or atanother device associated with the network. Any operable combination ofthe above are also considered a “mobile station.”

With reference now to FIG. 2, a schematic diagram illustrating variouscomponents of an example mobile device 200, which may be similar to themobile device 108 of FIG. 1, is shown. For the sake of simplicity, thevarious features/components/functions illustrated in the box diagram ofFIG. 2 are connected together using a common bus to represent that thesevarious features/components/functions are operatively coupled together.Other connections, mechanisms, features, functions, or the like, may beprovided and adapted as necessary to operatively couple and configure aportable wireless device. Furthermore, one or more of the features orfunctions illustrated in the example of FIG. 2 may be furthersubdivided, or two or more of the features or functions illustrated inFIG. 2 may be combined. Additionally, one or more of the features orfunctions illustrated in FIG. 2 may be excluded.

As shown, the mobile device 200 may include one or more local areanetwork transceivers 206 that may be connected to one or more antennas202. The one or more local area network transceivers 206 comprisesuitable devices, hardware, and/or software for communicating withand/or detecting signals to/from one or more of the LAN-WAPs 106 a-edepicted in FIG. 1, and/or directly with other wireless devices within anetwork. In some embodiments, the local area network transceiver(s) 206may comprise a WiFi (802.11x) communication transceiver suitable forcommunicating with one or more wireless access points; however, in someembodiments, the local area network transceiver(s) 206 may be configuredto communicate with other types of local area networks, personal areanetworks (e.g., Bluetooth® wireless technology), etc. Additionally, anyother type of wireless networking technologies may be used, for example,Ultra Wide Band, ZigBee, wireless USB, etc. In some embodiments, theunit 206 may be a receiver-only communication unit that can receivesignals (e.g., to enable navigational functionality) but cannot transmitsignals.

The mobile device 200 may also include, in some implementations, one ormore wide area network transceiver(s) 204 that may be connected to theone or more antennas 202. The wide area network (WAN) transceiver 204may comprise suitable devices, hardware, and/or software forcommunicating with and/or detecting signals from one or more of, forexample, the WAN-WAPs 104 a-c illustrated in FIG. 1, and/or directlywith other wireless devices within a network. In some implementations,the wide area network transceiver(s) 204 may comprise a CDMAcommunication system suitable for communicating with a CDMA network ofwireless base stations. In some implementations, the wirelesscommunication system may comprise other types of cellular telephonynetworks, such as, for example, TDMA, GSM, etc. Additionally, any othertype of wireless networking technologies may be used, including, forexample, WiMax (802.16), etc. In some embodiments, the unit 204 may be areceiver-only communication unit that can receive signals (e.g., toenable navigational functionality) but cannot transmit signals.

In some embodiments, an SPS receiver (also referred to as a globalnavigation satellite system (GNSS) receiver) 208 may also be includedwith the mobile device 200. The SPS receiver 208 may be connected to theone or more antennas 202 for receiving satellite signals. The SPSreceiver 208 may comprise any suitable hardware and/or software forreceiving and processing SPS signals. The SPS receiver 208 may requestinformation as appropriate from the other systems, and may perform thecomputations necessary to determine the position of the mobile device200 using, in part, measurements obtained by any suitable SPS procedure.

In some embodiments, the mobile device 200 may also include one or moresensors 212 coupled to a processor 210. For example, the sensors 212 mayinclude motion sensors (also referred to as inertial sensors) to providerelative movement and/or orientation information which is independent ofmotion data derived from signals received by the wide area networktransceiver(s) 204, the local area network transceiver(s) 206, and/orthe SPS receiver 208. By way of example but not limitation, the motionsensors may include an accelerometer 212 a, a gyroscope 212 b, ageomagnetic (magnetometer) sensor 212 c (e.g., a compass), an altimeter(e.g., a barometric pressure altimeter) 212 d, and/or other sensortypes. In some embodiments, the accelerometer 212 a may be implementedbased on micro-electro-mechanical-system (MEMS). Other types ofaccelerometers may be used in place of, or in addition to MEMS-basedaccelerometer. Additionally, a 3D accelerometer, sensitive to theaccelerations along three orthogonal axes, may be implemented. In someembodiments, the gyroscope 212 b may include a gyroscope based on MEMStechnology, and may be a single-axis gyroscope, a double-axis gyroscope,or a 3-D gyroscope configured to sense motion about, for example, threeorthogonal axes. Other types of gyroscopes may be used in place of, orin addition to MEMS-based gyroscope. In some embodiments, amagnetometer, configured to measure a magnetic field intensity and/ordirection (and, thus, may be configured to measure absolute orientationwith respect to the local magnetic fields) may also be implemented basedon MEMS technology. Such MEMS-based magnetometers may be configured todetect motion caused by the Lorentz force produced by a current througha MEMS conductor. Other types of magnetometers may also be used. Analtimeter may, for example, be configured to provide altitude data andthus may facilitate determining a floor in an indoor structure (e.g., ashopping mall) where the device may be located. Based on datarepresentative of altitude measurements performed by the altimeter,navigation tasks, such as obtaining assistance data (including maps) fora particular floor in the indoor structure may be performed. In someembodiments, absolute altitude may be available when a referencebarometer, at a known nearby location (e.g., in the same building wherethe mobile device 200 is located) is available. When such a referencebarometer is not available, a barometer can provide change of altitudeinformation, which can be used in conjunction with information frominertial sensors (e.g., the accelerometer, gyroscope, etc.) to, forexample, determine a position estimate.

The output of the one or more sensors 212 may be combined in order toprovide motion information. For example, estimated position of themobile device 200 may be determined based on a previously determinedposition and the distance traveled from that previously determinedposition as determined from the motion information derived frommeasurements by at least one of the one or more sensors. In someembodiments, the estimated position of the mobile device may bedetermined based on probabilistic models (e.g., implemented through aparticle filter, leveraging, for example, motion constraints establishedby venue floor plans, realized using the mobile device 200) using theoutputs of the one or more sensors 212. As further shown in FIG. 2, insome embodiments, the one or more sensors 212 may also include a camera212 e (e.g., a charge-couple device (CCD)-type camera), which mayproduce still or moving images (e.g., a video sequence) that may bedisplayed on a user interface device, such as a display or a screen.

The processor(s) (also referred to as a controller) 210 may be connectedto the local area network transceiver(s) 206, the wide area networktransceiver(s) 204, the SPS receiver 208, and/or the one or more sensors212. The processor may include one or more microprocessors,microcontrollers, and/or digital signal processors that provideprocessing functions, as well as other calculation and controlfunctionality. In some embodiments, a controller may be implementedwithout use of a processing-based device. The processor 210 may alsoinclude storage media (e.g., memory) 214 for storing data and softwareinstructions for executing programmed functionality within the mobiledevice. The memory 214 may be on-board the processor 210 (e.g., withinthe same IC package), and/or the memory may be external memory to theprocessor and functionally coupled over a data bus. Further detailsregarding an example embodiment of a processor or computation system,which may be similar to the processor 210, are provided below inrelation to FIG. 8.

A number of software modules and data tables may reside in memory 214and be utilized by the processor 210 in order to manage bothcommunications with remote devices/nodes (such as the various accesspoints depicted in FIG. 1), positioning determination functionality,and/or device control functionality. As will be described in greaterdetails below, the processor 210 may be configured, e.g., usingsoftware-based implementations, to enable determination, from signalsreceived from one or more transmitting devices, original (i.e.,unmodified) value(s) of controllably modified at least one signalparameter value (e.g., PHY-layer parameters). In the implementationsdescribed herein, the signals received at the receiving wireless devicemay have had their original signal parameter values (e.g., amplitude,etc.) modified in a controlled manner through application of adeterministic (and re-producible) pre-determined varyingsignal-modification process (e.g., a time-dependent dithering function)in order to prevent/inhibit unauthorized devices/applications/users fromperforming location determination operation using signals provided bythe transmitting devices. Thus, the receiving wireless device mayperform inverse operations (e.g., by applying inverse functions,provided a priori to the receiving device, to the varyingsignal-modification functions/processes applied at the transmittingnodes). Once the original values of the signal parameters have beenrecovered (and thus the distortion/perturbation controllably applied tothe signal at the source devices has been reversed), the position of thereceiving wireless device may be determined using the recovered signals(e.g., through fingerprint lookup and comparison procedures,multilateration-based procedures, etc.) The processor may also beconfigured to, in some implementations, derive a reconstructed value fora transmission characteristic, such as an antenna-based characteristic(e.g., an antenna selected from multiple antennas, relative phases andamplitudes of signals directed to the multiple antennas for beamsteering operations, cyclic delay, etc.), initially determined at atransmitting device according to at least one varying process (e.g., apseudorandom process). The transmission characteristic determined at thetransmitting device is used in order to, for example, inhibit locationdetermination operations by unauthorized users/applications/devices. Insituations where the device 200 has knowledge of the varying process(es)used by the transmitting device, it can derive a reconstructed value toenable it to perform location determination operations (e.g., performlocation determination operations more accurately than if the receivingdevice was not configured to determine the transmission characteristicvalue initially determined at the transmitting device).

The processor may also be configured to controllably modify values of atleast one signal parameter (e.g., PHY-layer parameters, such asamplitude, frequency, etc.) according to a pre-determined varying signalmodification process, and to transmit a signal with such modified valuesto another device (e.g., to an AP, to thus implement bi-directionaldithering of signals).

In some embodiments, the mobile device may include multiple antennas inelectrical communication to the one or more LAN transceivers 206 and/orthe one or more WAN transceivers 204 (in some variations, for each ofmultiple LAN transceivers and for each of multiple WAN transceivers,there may a corresponding separate antenna). The multiple antennas incommunication with the one or more transceivers may be configured toenable implementation of a pre-determined varying process (e.g., a timedependent pseudorandom process) to control/determine at least oneantenna-related transmission characteristic used to transmit signals.Implementation of such a pre-determined varying process to controlantenna-related transmission characteristics may thus enable ditheringof the signal transmitted so that only authorizedusers/applications/devices (e.g., authorized AP's with which the mobiledevice 200 is communicating) configured to reverse the antenna-basedvarying process, realized at the device 200 via the multiple antennasand the one or more transceivers, will be able to obtain correctmeasurements of the transmitted signal(s) required to perform accuratelocation determination.

In some embodiments, the transmission characteristic (e.g.,antenna-based transmission characteristic) may be the antenna(s)selected during a transmission interval to transmit the signals. Forexample, the antenna(s) through which a signal to be transmitted isdirected may be selected according to pre-determined varying antennaselection process (e.g., a pseudorandom process). A receiving wirelessdevice not configured to undither the transmitted signal that wasdithered according to the pre-determined varying antenna selectionprocess may therefore obtain skewed received signal measurements (e.g.,because the path followed by the transmitted signal will depend on theantenna selected, the estimated Channel Frequency Response (CFR), RSSI,RTT, etc., which can vary unpredictably). As a result, such a receivingdevice would not be able to perform accurate location determinationprocesses. In another example, respective relative phase and amplitudeof signals directed through the multiple antennas may be controlled(e.g., by the transceivers and/or the processor 210) according to one ormore pre-determined varying beam control processes (e.g.,pseudorandom-time-variation beam control processes) to control (e.g.,form and/or steer) a varying beam directed to the receiving device. Byvarying the beam according to such a pre-determined process that isknown only to authorized users/applications/devices, measurements ofsignal properties (e.g., RSSI, Angle of Arrival (AoA)) without knowledgeof that process will result in values that inhibit accuratedetermination of the location of the transmitting or receiving wirelessdevice. In a further example, a pre-determined process may be used todelay the various signals directed to the multiple antennas to thusimplement a varying (e.g., pseudorandom-time varying) cyclic delaydiversity implementation. In this case too, without knowledge of thevarying process(s) used to delay the various signals, accurate locationdetermination, based on measurements of signal properties performed atthe receiving device, is inhibited.

As further illustrated in FIG. 2, memory 214 may include a positioningmodule 216, an application module 218, a received signal strengthindicator (RSSI) module 220, and/or a round trip time (RTT) module 222.It is to be noted that the functionality of the modules and/or datastructures may be combined, separated, and/or be structured in differentways depending upon the implementation of the mobile device 200. Forexample, the RSSI module 220 and/or the RTT module 222 may each berealized, at least partially, as a hardware-based implementation, andmay thus include such devices as a dedicated antenna (e.g., a dedicatedRTT and/or RSSI antenna), a dedicated processing unit to process andanalyze signals received and/or transmitted via the antenna(s) (e.g., todetermine signal strength of a received signals, determine timinginformation in relation to an RTT cycle), etc.

The application module 218 may be a process running on the processor 210of the mobile device 200, which requests position information from thepositioning module 216. Applications typically run within an upper layerof the software architectures, and may include indoor navigationapplications, shopping applications, location-aware serviceapplications, etc. The positioning module 216 may derive the position ofthe mobile device 200 using information derived from various receiversand modules of the mobile device 200. For example, to determine themobile device's position based on RTT measurements, reasonable estimatesof MAC processing time delays introduced by each transmitting device(e.g., access point) may first be obtained and used to calibrate/adjustthe measured RTTs. The measured RTTs may be determined by the RTT module222, which can measure the timings of signals exchanged between themobile device 200 and the access points to derive round trip time (RTT)information. In circumstances where a transmitting device includes adelay according to a pre-determined varying signal modification process(e.g., a pseudorandom-time varying signal modification process), the RTTmodule, or another of the device's modules, may be configured todetermine the initial time value of the signal (e.g., without the delayadded according to the pre-determined varying signal modificationprocess). For example, an inverse process to the process that added thedelay would have to be performed on the received signal. In someembodiments, once measured, the RTT values may be passed to thepositioning module 216 to assist in determining the position of themobile device 200.

Other information that may be determined from communications received bythe mobile device 200 (e.g., using one of its transceivers) includes thereceived signal power, which may be represented in the form of RSSI(determined using the RSSI module 220). The RSSI module 220 may alsoprovide data regarding the signals to the positioning module 216. Whenusing RSSI measurements to determine a mobile device's position,appropriate calibration/adjustment procedures may need to be performed.Additionally, in circumstances where a transmitting device's Tx power ismodified, for example, the amplitude of the signal received by thedevice 200 (which would thus result in skewed RSSI measurements, at thereceiving station, that could lead to an incorrect positiondetermination), the device 200 may be configured to determine theoriginal amplitude value (e.g., transceiver Tx power) of the signal(e.g., prior to the pre-determined varying signal modification processperformed on an original value of a PHY-layer parameter(s) for a signalto be transmitted from the source transmitting device/node). Once thecorrect amplitude(s) of the received signal(s) is determined (and asubstantially correct RSSI value corresponding to the original,unmodified, PHY-layer parameter of the transmitted signals computed),the position of the device 200 may be determined Put another way, insuch embodiments, the AP Tx power is dithered and the computed RSSI atthe device (corresponding to a power that is less than the dithered APTx power) will show the same dithering pattern as that applied to theAP's transmitting power. The device 200 will thus be able to undo thedithering seen on the RSSI. A determined position of the mobile device200 may then be provided to the application module 218.

As further illustrated, the mobile device 200 may also includeassistance data storage 224 where assistance data may be stored,including data such as map information, data records relating tolocation information in an area where the device is currently located,etc. Assistance data may have been downloaded from a remote server. Insome embodiments, the mobile device 200 may also be configured toreceive supplemental information that includes auxiliary position and/ormotion data which may be determined from other sources (e.g., thesensors 212). Such auxiliary position data may be incomplete or noisy,but may be useful as another source of independent information forestimating the processing times of the WAPs. As illustrated in FIG. 2(using dashed lines), mobile device 200 may optionally store in memoryauxiliary position/motion data 226 which may be derived from informationreceived from other sources. Supplemental information may include, butnot be limited to, information that can be derived or based uponBluetooth® wireless technology signals, beacons, RFID tags, and/orinformation derived from a map (e.g., receiving coordinates from adigital representation of a geographical map by, for example, a userinteracting with a digital map).

The mobile device 200 may further include a user interface 250 whichprovides a suitable interface system, such as a microphone/speaker 252,keypad 254, and a display 256 that allows user interaction with themobile device 200. The microphone/speaker 252 provides for voicecommunication services (e.g., using the wide area network transceiver(s)204 and/or the local area network transceiver(s) 206). The keypad 254comprises suitable buttons for user input. The display 256 comprises asuitable display, such as, for example, a backlit LCD display, and mayfurther include a touch screen display for additional user input modes.

With reference now to FIG. 3, a schematic diagram of an exampletransmitting device, such as access point 300, which may be similar to,and be configured to have a functionality similar to that, of any of thevarious access points depicted in FIG. 1, is shown. The access point 300may include one or more transceivers 310 a-n electrically coupled to onemore antennas 316 a-n for communicating with wireless nodes, such as,for example, the mobile devices 108 or 200 of FIGS. 1 and 2,respectively. The each of the transceivers 310 a-310 n may include arespective transmitter 312 a-n for sending signals (e.g., downlinkmessages) and a respective receiver 314 a-n for receiving signals (e.g.,uplink messages). The access point may also include a network interface320 to communicate with other network nodes (e.g., sending and receivingqueries and responses). For example, each network element may beconfigured to communicate (e.g., wired or wireless backhaulcommunication) with a gateway, or other suitable entity of a network, tofacilitate communication with one or more core network nodes (e.g., anyof the other access points shown in FIG. 1, the positioning server 110,and/or other network devices or nodes). Additionally and/oralternatively, communication with other network nodes may also beperformed using the transceivers 310 a-n and/or the respective antennas316 a-n.

The access point 300 may also include other components that may be usedwith embodiments described herein. For example, the access point 300 mayinclude, in some embodiments, a communication controller 330 (which maybe similar to the processor 210 of FIG. 2) to manage communications withother nodes (e.g., sending and receiving messages) and to provide otherrelated functionality. For example, the controller 330 may be configuredto controllably modify values of at least one signal parameter (e.g.,PHY-layer parameters, such as amplitude, frequency, etc.) according to apre-determined varying signal modification process (such as apseudorandom-time-variation-based process). By modifying (e.g.,distorting/dithering) these parameters, an unauthorized party attemptingto use measurements of transmitted signals, but not knowing what processor function was used to modify the signals, would not be able todetermine the relationship between signal measurements taken at thereceiving device and the positions of the nodes sending the signalsreceived at the device, to thus perform position determination processto determine the device's approximate or exact position. In someembodiments, the controller 330, in conjunction with the one or moretransceivers 310 a-n and/or the antennas 316 a-n, are configured toimplement one or more pre-determined varying transmission characteristicprocesses that are used to transmit signals from the access point 300.As noted, in some embodiments, pre-determined varying antenna-basedtransmission characteristic determination processes may be implemented,including one or more of, for example, apseudorandom-time-variation-based antenna selection process to select atransmit antenna from multiple transmit antennas (e.g., one of antennas316 a-n), one or more pseudorandom-time-variation-based beam formingprocesses to controllably adjust corresponding relative phases andcorresponding amplitudes for each of multiple signals respectivelydirected to each of the multiple transmit antennas to control a varyingbeam, and/or one or more pseudorandom-time-variation-based cyclic delayprocesses to controllably adjust a corresponding delay added to at leastone of multiple signals respectively directed to at least one of themultiple transmit antennas. It is to be noted that the controlledmodification/determination of the transmission characteristics/signalparameters may be done, in some embodiments, without breaching orviolating required communication standards (e.g., without substantiallydeviating from any standardized communication requirements establishedfor such communication protocols as, for example, those related to IEEE802.11) and/or without modifying the data represented by the signals(e.g., so that the data represented by received signals can still bedetermined/decoded regardless of any modification to the PHY-layerparameters of the underlying signals, or of the transmissioncharacteristics used).

In some embodiments, the controller 330 may also be configured todetermine original signal parameter values of signals, received fromother wireless devices (e.g., from a personal mobile device), that weremodified according to some predetermined varying signal modificationprocess(es). For example, in some embodiments, an access point, such asthe AP 300 of FIG. 3, may be configured to track the position of apersonal wireless device. The personal wireless device may have applieda varying signal modification process (dithering process) toprevent/inhibit unauthorized servers or APs from tracking its location.However, an authorized server which was provided with information aboutthe signal modification process employed at the personal wireless device(e.g., was provided with the signal modification process/functionapplied at the personal wireless device, or was provided with the orinverse process/function corresponding to the process/function appliedat the personal wireless device) can be configured to determine themodified/dithered signals' original parameter values, to thus enable theauthorized server to track the personal wireless device's position. Insome embodiments, the controller 330 may further be configured toreconstruct the signal transmission characteristic value (e.g.,antenna-based transmission characteristic value) that was determined andused at a transmitting device (e.g., a mobile device in communicationwith the access point 300). Thus, for example, in some embodiments, theaccess point 300 (e.g., through the controller 330, in conjunction withthe device's transceivers and antennas) may be configured to receiving asignal transmitted from another wireless device (where that other deviceincludes multiple transmit antennas) using at least one signaltransmission characteristic initially determined at the other wirelessdevice according to at least one pre-determined varying transmissioncharacteristic determination process, with the at least one signaltransmission characteristic including one or more of, for example, atransmit antenna selected from the multiple transmit antennas, a beamcharacteristic, and/or a cyclic delay diversity parameter. The accesspoint 300, in such embodiments, may also be configured to derive areconstructed value of the at least one signal transmissioncharacteristic initially determined at the other wireless device, anddetermine a position of the wireless device based, at least in part, onthe derived reconstructed value of the at least one signal transmissioncharacteristic initially determined at the other wireless deviceaccording to the at least one pre-determined varying transmissioncharacteristic determination process. For example, the access point 300may be configured to determine the particular antenna(s) from thetransmitting device's multiple antennas that was used by thetransmitting device to transmit the signals to the access point 300.Knowing the particular antenna(s) can thus enable the access point 300to have more accurate information about the path traveled by the signalit received, and thus to more accurately determined location informationin relation to the transmitting device and/or the access point 300.

In addition, the access point 300 may include, in some embodiments,neighbor relations controllers (e.g., neighbor discovery modules) 340 tomanage neighbor relations (e.g., maintaining a neighbor list 342) and toprovide other related functionality. The communication controller may beimplemented, in some embodiments, as a processor-based device, with aconfiguration and functionality similar to that shown and described inrelation to FIG. 8.

With reference to FIG. 4, a flowchart of an example procedure 400 usedfor location determination operations is shown. The operations depictedin FIG. 4 are generally performed at a device/node (which may be similarto any of the WAP's 104 a-c and 106 a-e depicted in FIG. 1 or the accesspoint 300 depicted in FIG. 3) transmitting signals that are used byreceiving devices to perform, among other operations, positiondetermination. In some embodiments, the procedure 400 may also beperformed at a personal wireless device (such as the 108 or 200 of FIGS.1 and 2, respectively).

An original unmodified value of at least one PHY-layer signal parameterfor a signal that is to be transmitted from a first wireless device (thetransmitting device) is controllably modified 410 according to apre-determined varying signal modification process (e.g., obtain ordetermine the original unmodified value of the PHY-layer signalparameter, and apply the varying signal modification process to thatoriginal unmodified value). As noted, in some embodiments, the PHY-layersignal parameters of the signal include, for example, the amplitude(also referred to as the transmit power, or Tx), the signal's timestamp,a center frequency, gain, signal equalization, and/or any combinationthereof. As also noted, the pre-determined varying signal modificationprocess is configured to modify the at least one signal parameter (andin some embodiments, two or more parameters that may each be modifiedaccording to a different process), generally without affecting contentencoded by the signal, in a controlled manner that is known to anauthorized user/device, but not known to an unauthorized user/device.Table 1 below provides examples of some of the different signalparameters that may be dithered and what effect such dithering has onthe ability to determine position of a receiving device (Table 1 alsoincludes antenna-based characteristics that can be controlled to inhibitlocation determination by unauthorized users/applications/devices).

TABLE 1 # Parameter Description Effect/Purpose 1 Tx power Transmissionpower Defeat/inhibit RSSI fingerprinting, RSSI- (amplitude). basedmultilateration procedures, and positioning processes. 2 Tx equalizerChange the Tx gain Defeat/inhibit channel-impulse response on each OFDM(CIR) position fingerprinting based subcarrier. approaches.Defeat/inhibit speed estimation via fast fading statistics or relatedapproaches. Confuse Time of Arrival (TOA) procedures/ techniques byblurring TOA edges. Confuse Angle of Arrival (AoA) procedures inMultiple-Input Multiple-Output (MIMO) systems. 3 Timestamps Dither atimestamp Defeat/inhibit RTT or Rx (e.g., AP beacon) value inserted intoOWPT (One-way Propagation Time) outgoing packets. estimation. 4 Tx timeRandom Defeat/inhibit RTT and Rx (e.g., AP advance/delay of beacon) OWPTestimation. actual RF transmission time relative to a timestamp insertedinto outgoing packets. 5 Center frequency Dither the Tx centerDefeat/inhibit Doppler-based aiding (for frequency. fast movingvehicles) approaches. 6 Antenna Selection Using a pseudo- Will have atleast some of the same effects random sequence, as those described inrows 1-4 above. select one of many antennas to use for transmission. 7Relative phase Dither antenna beam Will have at least some of the sameeffects and amplitude forming/steering. as those described in rows 1-4above. directed to multiple transmit antennas 8 Cyclic delay Cause atime-varying Will have at least some of the same effects diversitychannel frequency as those described in rows 1-4 above. parameterresponse (CFR).

In some embodiments, controllably modifying the original unmodifiedvalue of the at least one signal parameter according to at least onepre-determined varying signal modification process may includecontrollably modifying the original unmodified value of the at least onePHY-layer signal parameter according to a pseudorandom-process.

In some embodiments, controllably modifying the original/initial valueof the at least one signal parameter according to at least onepre-determined varying signal modification process may includecontrollably modifying the original unmodified value of the at least onePHY-layer signal parameter according to an autoregressive moving averageprocess. In some embodiments, an autoregressive moving average (ARMA)filter may be used with a pseudorandom process in the following manner.A pseudo-random generator may generate a sequence of random numbers(typically a sequence of −1s and +1s) that is sent into an ARMA filterthat can be implemented digitally. The output is a slowly moving output,that can be added to, for example, the nominal Tx power, the timestamp,the frequency, the nominal MAC processing delay (i.e., the RTTturn-around time at the AP), etc. The architecture used for this processmay be:

-   -   pseudo-random generator.    -   ARMA process equivalent z-transform (e.g., a polynomial fraction        with different powers of z⁻¹ representing different delays).    -   The parameters of the randomization process may include:        -   a seed value to be injected in the pseudo random generator,        -   a start time,        -   a sample period at which the pseudo-random generator and the            ARMA process will be updated, and        -   a scaling coefficient that will multiply the ARMA raw output            to control the amplitude of this random term.

Thus, in such embodiments, controllably modifying the originalunmodified value of the at least one PHY-layer signal parameteraccording to the autoregressive moving average process may includegenerating a sequence of random numbers based on a pseudorandomgenerator process, inputting the sequence of random numbers to az-transform implementation of the autoregressive moving average processto generate a resultant sequence, and modifying the original unmodifiedvalue of the at least one PHY-layer signal parameter (e.g., amplitude,frequency, gain, phase, etc.) based on the resultant sequence.

It is to be noted that some WiFi measurements may have functionalrelation to others. For instance, RSSI and range (or delta (Δ) RSSI anddelta (Δ) RTT) may be related. Thus, under some circumstances, a partymay be able to deduce the dithering sequence of, for example, RSSI, ifthe RTT is left un-dithered (and vice versa). Also, it may be possibleto deduce the dithering sequence if two measurable values (e.g., RSSIand RTT) are dithered with exactly the same varying signal modificationprocess (e.g., with the same autoregressive sequence). Thus, it may bedesirable to use different dithering functions/processes for differentmeasurables. Accordingly, in some embodiments, controllably modifyingthe original unmodified value of the at least one PHY-layer signalparameter according to at least one pre-determined varying signalmodification process may include controllably modifying each originalunmodified value of two or more PHY-layer signal parameters according torespective different pre-determined varying signal modificationprocesses.

With continued reference to FIG. 4, the signal with the controllablymodified value of the at least one PHY-layer signal parameter istransmitted 420 (e.g., through one of various transceivers ortransmitter devices) to a second wireless device (e.g., a receivingwireless device such as the device 108 of FIG. 1 or the device 200 ofFIG. 2). The transmitted signal is configured to facilitate positiondetermination at/for the second wireless device when the originalunmodified value of the at least one PHY-layer signal parameter isdetermined at the second wireless device from the controllably modifiedvalue of the at least one PHY-layer signal parameter. To determine theoriginal value of the controllably modified at least one signalparameter of the received signal, the receiving device would need toknow the process/function that was used at the transmitting device tovary the signal (e.g., to dither it) and/or to know/determine an inverseprocess/function that needs to be applied to the received signal inorder to recover the original value(s) (e.g., the original/initialvalues prior to modification by a varying process at the transmittingdevice/node) of the at least one signal parameter.

For example, in embodiments in which the varying signal modificationprocess used at the transmitting device is a autoregressive movingaverage process, information such as the pseudorandom seed, scalingamplitude, starting time, etc., are provided to the authorized receivingdevice (e.g., in a secure manner at some earlier time preceding thedithered transmission). An un-dithering (i.e., inverting) process maythus include, in some embodiments, starting an equivalent pseudo-randomprocess at the receiving device that will deliver the same digitalsequence as the one used at the transmitting device (e.g., at the AP) assoon as the same seed and scaling factor are injected, and bothsequences are synchronized in time. The receiving device can thensubtract from the measurement the scaled output of the ARMA process. Inthis example, synchronization can be done in absolute mode (millisecondaccuracy time of day can be easily obtained at the mobile over NTP orthe cellular network), or by resynchronizing both processes. Absolutetime synchronization accuracy may be loose (e.g., on the order of onesecond), as the synchronization needs to be done as a fraction of thesampling period (which is on the order of several seconds, with aperiodicity of several minutes). This is because a dithering ARMAprocess is configured to have a slowly changing output, and thereforethe absolute time clocks at the transmitting device and receiving devicedo not have to be very accurately synchronized for the un-dithering atthe receiving device to work well. Incorrect synchronization mayengender a graceful degradation, as the very slowly evaluating outputprovides a high correlation of the outputs, even for intervals severaltimes longer than the sampling period. In this example, the net effectof dithering may be a slowly varying “natural-looking” physicalphenomenon that will wander around the true value during a timesubstantially equal to the PRN sequence (this may be similar to theeffect of ionosphere errors in GNSS). Because dithering functionsgenerally are not synchronized across AP's, and because the estimatedposition depends on the measurement contributions of each AP, theeffective repetition period of the 2D position error pattern will be theproduct of the dithering periods of all the AP's used for a positionfix.

Recovered original value(s) of the at least one PHY-layer signalparameter at the receiving device can thus be used to determine positionof the receiving device. For example, metrics such as RSSI and/or RTTcan be derived from the recovered original values of the signalparameters of the signals received from one or more access points (eachof which may be identified by an access point identifier, such as aunique MAC address associated with the access point), or from othertypes of transmitters, and those metrics may be used to determine anestimate of the second (receiving) wireless device's location. Forexample, a database (which may be stored locally or at a remotedevice/system), containing geographic locations, processing delays,power profiles, RTT profiles, and other such information for multipletransmitting device (e.g., access points) with known geographicalpositions, may be accessed and relevant data (e.g., for particulartransmitters/access points from which signals at the receiving devicewere received) may be obtained. The database data so obtained may beused to facilitate location determination of the receiving device. Forexample, the relative distances of the receiving device from thetransmitting devices (access points) transmitting the signals may bedetermined based, at least in part, on known locations for thosetransmitters/access points stored on the accessed database, and anestimation of the location of the device may be computed/derived (e.g.,using multilateration procedures, such as a trilateration procedure). Insome embodiments, the position of the mobile device may be also bedetermined, for example, by comparing the actual measured values ofsignal strength (or RSSI) and/or RTT obtained from one or moretransmitting device (access points) to stored profiles to identify aprofile matching (approximately or precisely) the set of metric valuesdetermined by the receiving device (this location determinationprocedure is also referred to as a “fingerprinting” procedure). It is tobe noted that, in some embodiments, database(s) for RSSI and/or RTTfingerprints could be created using RF propagation models (e.g., thattake into account wall geometry). In such embodiments it is usuallynecessary to get at least some real survey measurements in order toproperly calibrate the parameters used by the RF propagation model. Alocation estimate associated with a matching stored profile may then bedeemed to be an estimate of the current location of the receiving devicethat received the transmitting devices'/access points' signals. Thus, insome embodiments, the transmitted signal configured to facilitateposition determination at the second wireless device is configured tofacilitate position determination at the second wireless device based onone or more of, for example, a received signal strength indicator(RSSI)-based positioning determination process, a round trip time(RTT)-based position determination process, and/or a speed-basedposition determination process aided by an inertial navigation system.In some embodiments, the RSSI-based position determination process mayinclude an RSSI-fingerprinting process. In some embodiments, theRTT-based position determination process may include anRTT-fingerprinting process.

In some embodiments, a transmitting device (such as an AP) may use asingle dithering sequence for all its transmissions. However, this maynot prevent/inhibit unauthorized parties from collecting un-ditheredfingerprints. For example, a static reference STA may collect the sameWiFi frames and measurements that are collected simultaneously by arover STA. In a post-processing step, correction values for each timeepoch can be determined by the static STA data collected. Thesecorrection values are then applied to the rover STA data set. This mayenable determining (and thus removing) the dithering that is common toboth data sets. A similar approach could be used for real-timepositioning that is analogous to the RTCM (Real-Time Correction Message)used in D-GPS and RTK positioning. Real-time WiFi measurementscorrection information could be transmitted to clients using somethingsimilar to the NTRIP HTTP-based protocol for GNSS. However, if atransmitting device applies a unique varying signal modification processto unicast frames directed to a specific receiving STA (regardless ofwhether different dithering or other varying signal modificationprocesses are applied to different parameters of the transmittedsignals), and a different dithering process to another receivingstation, the reference station would have to transmit dither correctionvalues for every signal to the receiving STA. This may present achallenge when performed at a large scale.

In private/stand-alone APs, management of signal modification processesto modify PHY-layer parameters may be such that signal parameters aregenerated using some hash function based on a security password thatneeds to be established during setup of the AP. If the AP is to beusable for location determination functionality, but for authorizedusers only, the AP may broadcast these parameters (includingbroadcasting, for example, actual dithering/varying signal modificationfunctions) in its WiFi beacons in an encrypted form, or a central servermay collect this information from the AP during setup, and onlyauthorized users may then access this information.

With reference now to FIG. 5, a flowchart of an example procedure 500used for location determination using dithered signals is shown. Theoperations depicted in FIG. 5 are generally performed at a devicereceiving signals that are used to perform position determination. Theprocedure 500 includes receiving 510 (e.g., using one of varioustransceivers or receivers) at a first wireless device (which may besimilar to the device 108 or the device 200 depicted in FIGS. 1 and 2,respectively) a signal, transmitted from a second wireless device (suchas an AP), with a controllably modified at least one PHY-layer signalparameter value that was generated according to at least onepre-determined varying signal modification process applied to anoriginal unmodified value of the at least one PHY-layer signalparameter. The at least one PHY-layer signal parameter includes, forexample, amplitude, frequency, timestamp, gain, signal equalization,and/or any combination thereof. In some embodiments, the receivingdevice may be an AP, such as any of the AP's 104 a-c, or 106 a-e of FIG.1 (implementing undithering processes in AP's may thus enablerealization of, for example, bi-directional dithering implementations,or realization of device tracking functionality implemented throughAP's).

An original unmodified value of the at least one PHY-layer signalparameter value is determined 520 from the received signal (e.g., byapplying to the received signal, or its decoded value, an inverseprocess/function which was provided to the receiving device at anearlier time). Having determined the original value(s) of the at leastone PRY-layer signal parameter, a position of the first wireless deviceis determined 530 based, at least in part, on the original unmodifiedvalue of the at least one PHY-layer signal parameter of the signal,determined from the controllably modified at least one PHY-layer signalparameter value of the signal received at the first wireless device. Forexample, various location determination procedures (e.g.,fingerprinting, multilateration, etc.) may be performed on theundithered PHY-layer values determined by the receiving device.

As noted, in some embodiments, further dithering operations to inhibitlocation determination functionality by unauthorizedusers/applications/devices may be performed through application ofpre-determined varying process(es) to determine signal transmissioncharacteristics (such as antenna-based transmission characteristics)that are used to transmit signals from one wireless device to another.In some embodiments, the signal transmitted may not include informationabout the transmission characteristics that were controlled according tothe pre-determined varying process (for example, the signal itself maynot include information about which antenna was selected, what relativephases and amplitudes were directed to the transmitter's multipleantennas that resulted in particular beam features, etc.), and thus thereceiving device would need to have knowledge about the particularvarying process(es) used in order to compensate for the transmissioncharacteristics used at the transmitting device. In some embodiments,information about the values of the transmission characteristics and/orthe varying processes used may be includes in the signal (e.g., asencrypted information).

Accordingly, with reference to FIG. 6, a flowchart of an exampleprocedure 600 to control/determine transmission characteristics isshown. The procedure 600 includes determining 610, at a first wirelessdevice (e.g., an AP such as a WiFI AP) comprising multiple transmitantennas, at least one signal transmission characteristic according toat least one pre-determined varying transmission characteristicdetermination process, with the at least one transmission characteristicincluding, for example, a transmit antenna selected from the multipletransmit antennas, a beam characteristic, a cyclic delay diversityparameter, or any combination thereof. As noted, determining the atleast one signal transmission characteristic according to the at leastone pre-determined varying transmission characteristic determinationprocess may include determining the at least one signal transmissioncharacteristic according to at least one autoregressive moving averageprocess. In such embodiments, implementing an autoregressive movingaverage process may include generating a sequence of random numbersbased on a pseudorandom generator process, inputting the sequence ofrandom numbers to a z-transform implementation of the at least oneautoregressive moving average process to generate a resultant sequence,and determining the at least one signal transmission characteristicbased on the resultant sequence. Additionally, clocks at the firstwireless device and the second wireless device may be synchronizedrelative to a reference time, and a second pseudorandom number sequenceat the second wireless device may be generated such that the secondpseudorandom number sequence is synchronized with the sequence of randomgenerated at the first wireless device.

In some embodiments, determining the at least one signal transmissioncharacteristic may include determining the at least one signaltransmission characteristic according to at least onepseudorandom-time-variation-based process. For example, the transmitantenna(s) to be used at particular time instances may be determinedaccording to a pseudorandom-time-variation-based antenna selectionprocess. In some embodiments, the varyingpseudorandom-time-variation-based antenna selection may be such thatmore than one antenna is selected to simultaneously transmit signalsthrough the selected antennas. In another example, the at least onevarying pseudorandom-time-variation-based process may include multiplevarying processes applied to determine/adjust the relative phases andamplitudes for each of multiple signals respectively directed to each ofthe multiple transmit antennas of the transmitting device (e.g., controlthe vector of phases and vector of amplitudes). By controlling thephases and amplitudes of the signals directed to the multiple antennas,beam steering attributes for the radiation pattern resulting fromtransmission of signals via the multiple antennas (e.g., control thedirection and/or shape of the main lobe of the radiation patternresulting from the transmission through the multiple antennas) can thusbe controlled. Controlling the direction and/or shape of the main lobeof the radiation pattern through varying processes (e.g., pseudorandomprocesses) that is not known to unauthorized users/applications/devicesprovides another way to dither signals in such a way that accuratelydetermining the location of a wireless device is inhibited. In yet afurther example, the at least one varyingpseudorandom-time-variation-based process may be used to implement acyclic delay diversity functionality. Thus, in such implementations,cyclic delay durations for different signals (e.g., for different OFDMsymbols) may be selected according to, for example, apseudorandom-time-variation-based process that is known at the receivingwireless device, but not known to unauthorizedusers/applications/devices.

With continued reference to FIG. 6, the at least one transmissioncharacteristic determined according to the at least one pre-determinedvarying transmission characteristic is used to transmit 620 a signalfrom the first wireless device to a second wireless device (e.g., amobile device). The transmitted signal is configured to facilitateposition determination of the second wireless device (or some otherwireless device) upon deriving reconstructed value of the at least onesignal transmission characteristic determined at the first wirelessdevice (i.e., upon deriving at the second wireless device areconstructed value of the at least one signal transmissioncharacteristic that was initially determined at the first wirelessdevice). Generally, without knowing what varying process was used at thefirst (transmitting) device to determine the transmission characteristicused at the first wireless device when the signal was transmitted, thereceiving device does not have complete or accurate information thatwould be required to accurately perform location determinationfunctionality. For example, without knowing what antenna(s) was selectedfrom a transmitting device's multiple antennas, the receiving devicewould have difficulty compensating for the variations in the pathtraversed by the transmitted signal (i.e., the channel). In someembodiments, the transmitted signal configured to facilitate positiondetermination of the second wireless device (or some other device) maybe configured to facilitate position determination of the secondwireless device based on one or more of, for example, a received signalstrength indicator (RSSI)-based positioning determination process, around trip time (RTT)-based position determination process, and/or aspeed-based position determination process aided by an inertialnavigation system.

In some embodiments, in addition to controlling at least oneantenna-based transmission characteristics according to at least onevarying transmission characteristic determination process (e.g., apseudorandom process), a transmitting device may also be configured tocontrollably modify an original unmodified value of at least onePHY-layer parameter of the signal to be transmitted, such as thesignal's amplitude, frequency, timestamp, gain, signal equalization,delay, signal phase, and/or any combination thereof.

As also noted, in some embodiments, the first (transmitting) device mayinclude an access point, such as a WiFi access point, and the second(receiving) wireless device may include a preauthorized wireless deviceequipped with an undithering integrated circuit configured to enableundithering of the signal transmitted from the first wireless deviceusing the at least one signal transmission characteristic determinedaccording to the at least one pre-determined varying determinationprocess.

With reference now to FIG. 7, a flowchart of an example procedure 700 toperform location determination using dithered signals is shown. Theprocedure 700 includes receiving 710 at a first wireless device (e.g., apersonal mobile device, such a cell phone) a signal transmitted from asecond wireless device (e.g., an AP) that includes multiple transmitantennas using at least one signal transmission characteristic initiallydetermined at that other wireless device according to at least onepre-determined varying transmission characteristic determinationprocess. The at least one signal transmission characteristic includes,for example, a transmit antenna selected from the multiple transmitantennas, a beam characteristic, a cyclic delay diversity parameter,and/or any combination thereof. As noted, in some embodiments, the atleast one signal transmission characteristic, initially determinedaccording to the at least one pre-determined varying transmissioncharacteristic determination process, may include the transmit antennaselected at the second wireless device from the multiple transmitantennas according to a pseudorandom-time-variation-based antennaselection process, a corresponding relative phase and a correspondingamplitude for each of multiple signals, respectively directed to each ofthe multiple transmit antennas to control a varying beam, that arecontrollably adjusted at the second wireless device according to one ormore pseudorandom-time-variation-based beam forming processes, and/or acorresponding delay added to at least one of multiple signals,respectively directed to at least one of the multiple transmit antennas,controllably adjusted at the second wireless device according to arespective at least one pseudorandom-time-variation-based cyclic delayprocess.

The procedure 700 further includes deriving 720 at the first wirelessdevice a reconstructed value of the at least one signal transmissioncharacteristic initially determined at the second wireless device, anddetermining 730 a position of the first wireless device based, at leastin part, on the derived reconstructed value of the at least one signaltransmission characteristic initially determined at the second wirelessdevice according to the at least one pre-determined varying transmissioncharacteristic determination process.

In some embodiments, the procedure 700 may further include determiningfrom the received signal an original value (i.e., prior to beingmodified by a pre-determined varying modification process) of at leastsecond signal transmission characteristics, e.g., a PHY-layer signalparameter that is controllably modified at the second wireless deviceaccording to at least one pre-determined varying transmissioncharacteristic modification process. The at least second signaltransmission characteristic may include, for example, signal amplitude,signal frequency, signal timestamp, signal gain, signal equalization,signal delay, signal phase, and/or any combination thereof.

Performing the procedures to determine transmission characteristics(e.g., modify/dither signal parameters of a signal) to recover originalvalues of such transmission characteristics (e.g., at a receivingdevice), and/or to determine position of a wireless device receivingsuch dithered signals, may be facilitated by a processor-based computingsystem. With reference to FIG. 8, a schematic diagram of an examplecomputing system 800 is shown. The computing system 800 may be housedin, for example, a handheld mobile device such as the devices 108 and200 of FIGS. 1 and 2, respectively, a transmitting device, such as theaccess points 104 a-c and 106 a-e depicted in FIG. 1 or the access point300 depicted in FIG. 3, etc. The computing system 800 includes aprocessor-based device 810 such as a personal computer, a specializedcomputing device, and so forth, that typically includes a centralprocessor unit 812. In addition to the CPU 812, the system includes mainmemory, cache memory and bus interface circuits (not shown). Theprocessor-based device 810 may include a mass storage device 814, suchas a hard drive and/or a flash drive associated with the computersystem. The computing system 800 may further include a keyboard, orkeypad, 816, and a monitor 620, e.g., a CRT (cathode ray tube) or LCD(liquid crystal display) monitor, that may be placed where a user canaccess them (e.g., a mobile device's screen).

The processor-based device 810 is configured to, for example, implementthe procedures and methods described herein, including procedures tocontrollably modify at least one PHY-layer signal parameter according toat least one pre-determined varying signal modification process,determine at least one transmission characteristic (e.g., antenna-basedtransmission characteristic) according to a pre-determined varyingprocess, recover original values of signal parameters/transmissioncharacteristics controlled according to varying processes/functions,and/or perform position determination operations. The mass storagedevice 814 may thus include a computer program product that whenexecuted on the processor-based device 810 causes the processor-baseddevice to perform operations to facilitate the implementation of theabove-described procedures.

The processor-based device may further include peripheral devices toenable input/output functionality. Such peripheral devices may include,for example, a CD-ROM drive and/or flash drive, or a network connection,for downloading related content to the connected system. Such peripheraldevices may also be used for downloading software containing computerinstructions to enable general operation of the respectivesystem/device. Alternatively and/or additionally, in some embodiments,special purpose logic circuitry, e.g., an FPGA (field programmable gatearray), a DSP processor, or an ASIC (application-specific integratedcircuit) may be used in the implementation of the computing system 800.Other modules that may be included with the processor-based device 810are speakers, a sound card, a pointing device, e.g., a mouse or atrackball, by which the user can provide input to the computing system800. The processor-based device 810 may include an operating system.

Computer programs (also known as programs, software, softwareapplications or code) include machine instructions for a programmableprocessor, and may be implemented in a high-level procedural and/orobject-oriented programming language, and/or in assembly/machinelanguage. As used herein, the term “machine-readable medium” may referto any non-transitory computer program product, apparatus and/or device(e.g., magnetic discs, optical disks, memory, Programmable Logic Devices(PLDs)) used to provide machine instructions and/or data to aprogrammable processor, including a non-transitory machine-readablemedium that receives machine instructions as a machine-readable signal.

Memory may be implemented within the processing unit or external to theprocessing unit. As used herein the term “memory” refers to any type oflong term, short term, volatile, nonvolatile, or other memory and is notto be limited to any particular type of memory or number of memories, ortype of storage media upon which memory is stored.

If implemented in firmware and/or software, the functions may be storedas one or more instructions or code on a computer-readable medium.Examples include computer-readable media encoded with a data structureand computer-readable media encoded with a computer program.Computer-readable media includes physical computer storage media. Astorage medium may be any available medium that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, semiconductor storage, or other storagedevices, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer; disk and disc, as used herein, includes compactdisc (CD), laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

Some or all of the subject matter described herein may be implemented ina computing system that includes a back-end component (e.g., as a dataserver), or that includes a middleware component (e.g., an applicationserver), or that includes a front-end component (e.g., a client computerhaving a graphical user interface or a Web browser through which a usermay interact with an embodiment of the subject matter described herein),or any combination of such back-end, middleware, or front-endcomponents. The components of the system may be interconnected by anyform or medium of digital data communication.

The computing system may include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and servergenerally arises by virtue of computer programs running on therespective computers and having a client-server relationship to eachother.

Further Applications and Uses

In some jurisdictions, it may be illegal to collect MACIDs and associatethese with a geographical location. Typically, nearby GPS fixes areassociated with the MACID (obtained for example via crowdsourcing fromvehicles and/or pedestrians passing by). By using the methods andprocedures described herein, it may become more difficult to obtain APposition estimates that are more accurate than the nearby GPS fixes.Thus, the procedures/methods/techniques described herein may beconfigured to be turned on by default in stand-alone personal andcommercial APs in some jurisdictions. A private AP owner may want todeny the usage of his/her AP for location determination purposes. Inaddition to the “hidden BSSID” check mark (or coupled with it), theremay be a check mark to deny or allow the usage of this AP for locationdetermination (e.g., an end-user configurable AP option that may beactivated or deactivated by, for example, setting/unsetting a checkboxnext to the description of the option on a configuration web page forthe particular AP). The checkmark could automatically trigger the setupof default dithering parameters. For instance, the dithering processseed and other parameters could be calculated automatically from thenetwork SSID and passphrase (the user might also have the option ofsetting these parameters manually).

In some embodiments, users of WiFi-equipped devices such as smartphonesmay wish to make it more difficult for network-based positioning systemto track them. Probes originating from the infrastructure APs could beresponded to using the dithering varying-signal-modification processesdescribed herein. Thus, in some embodiments, a person's handheld device(such as a mobile device) may be configured to apply a varying signalmodification process to controllably modify an original unmodified valueof at least one PHY-layer parameter of a signal transmitted by thedevice. For example, transmission power of a signal to be transmitted bysuch a handheld device may be controlled according to a varyingmodification process (e.g., a position or time dependent process, suchas a pseudorandom-time-variation-based process), a delay with a lengthdetermined according to a varying process may be added to the signal,etc. The signal whose PHY-layer parameters(s) have been modified in sucha manner will thus inhibit or interfere with position tracking processesto track its position by unauthorized access points that do not haveinformation about the varying process(es) that would be required torecover the original unmodified value of the signals they receive fromthe mobile device. While the controllable modification of PHY-layerparameters of signals transmitted by the mobile device is used tointerfere with or inhibit the ability of access points receiving thesignals to track the position of a transmitting mobile device, contentdata included or represented by those signals may remain unmodified.

In some embodiments, personal devices such as mobile phones or tabletsmay implement peer-to-peer positioning estimation and reportingfeatures. These could be based, at least in part, on peer-to-peer rangeestimation (e.g., using RSSI or RTT). Certain users may want to denypeers access to accurate range information and allow only coarseproximity information. Some users may thus elect to prevent accuraterange estimation by peers by implementing/activating controllable signalmodification features similar to those described herein.

In some embodiments, a venue owner may want to block any and all personsfrom getting any useful measurements from the venue AP's for positioningpurposes (e.g., populating a WiFi fingerprint DB), or for any otherpurpose. This might be done for local privacy policy or governmentalregulatory reasons. The venue owner's managed network may thus deployAP's configured to perform controllable modification of signals'PHY-layer parameters in the manner described herein. For example, incircumstances where the access points deployed include WiFi accesspoints, those access points may be configured to perform WiFi dithering.The feature could then be activated in each AP from a centralizednetwork controller (such a controller may be implemented on a serversuch as the server 110 depicted in FIG. 1). The control of the ditheringprocess(es) (e.g., some predetermined autoregressive moving average(ARMA) process/function) and their parameters (amplitude, frequency, andso forth) may be performed from the controller. The parameterizationcould be changed at will and as often as desired from the controller.

In some embodiments, a venue owner may want to limit the access toindoor location to his authorized customers/clients applications and tolimit analytics to its own internal use. A predetermined varying signalmodification process/function (e.g., a compact representation of adithering function for each AP, represented, for example, as astate-space model, and associated parameters for each such function)could be communicated in a secure way to authorized clients/customers.This information could be bundled with other assistance data (AD), suchas floor maps or RSSI/RTT heat maps, etc. Alternatively and/oradditionally, the dithering function(s) and parameters might be embeddedin a secure way in proprietary and encrypted AP beacon data elements.The client device will then be able to apply inverse functions/processeson the controllably modified (dithered) signals it receives in order toremove the effect of the dithering from the measurements of interest.

Although particular embodiments have been disclosed herein in detail,this has been done by way of example for purposes of illustration only,and is not intended to be limiting with respect to the scope of theappended claims, which follow. In particular, it is contemplated thatvarious substitutions, alterations, and modifications may be madewithout departing from the spirit and scope of the invention as definedby the claims. Other aspects, advantages, and modifications areconsidered to be within the scope of the following claims. The claimspresented are representative of the embodiments and features disclosedherein. Other unclaimed embodiments and features are also contemplated.Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. A method comprising: controllably modifying, at afirst wireless device, an original unmodified value of at least onePHY-layer signal parameter for a signal according to at least onepre-determined varying signal modification process, the at least onePHY-layer signal parameter comprising: amplitude, frequency, timestamp,gain, signal equalization, or any combination thereof; and transmitting,to a second wireless device, the signal with a controllably modifiedvalue of the at least one PHY-layer signal parameter, the transmittedsignal configured to facilitate position determination of the secondwireless device when the original unmodified value of the at least onePHY-layer signal parameter is determined at the second wireless devicefrom the controllably modified value of the at least one PHY-layersignal parameter.
 2. The method of claim 1, wherein controllablymodifying the original unmodified value of the at least one PHY-layersignal parameter according to the at least one pre-determined varyingsignal modification process comprises: controllably modifying originalunmodified values of two or more PHY-layer signal parameters accordingto respective different pre-determined varying signal modificationprocesses.
 3. The method of claim 2, wherein one of the two or morePHY-layer signal parameters comprises at least one of: delay or phase.4. The method of claim 1, wherein controllably modifying the originalunmodified value of the at least one PHY-layer signal parameteraccording to the at least one pre-determined varying signal modificationprocess comprises: controllably modifying the original unmodified valueof the at least one PHY-layer signal parameter according to apseudorandom-time-variation-based process.
 5. The method of claim 1,wherein controllably modifying the original unmodified value of the atleast one PHY-layer signal parameter according to the at least onepre-determined varying signal modification process comprises:controllably modifying the original unmodified value of the at least onePHY-layer signal parameter according to an autoregressive moving averageprocess.
 6. The method of claim 5, wherein controllably modifying theoriginal unmodified value of the at least one PHY-layer signal parameteraccording to the autoregressive moving average process comprises:generating a sequence of random numbers based on a pseudorandomgenerator process; inputting the sequence of random numbers to az-transform implementation of the autoregressive moving average processto generate a resultant sequence; and modifying the original unmodifiedvalue of the at least one PHY-layer signal parameter based on theresultant sequence.
 7. The method of claim 6, wherein respective clocksat the first wireless device and the second wireless device aresynchronized relative to a reference time, and wherein a secondpseudorandom number sequence at the second wireless device is generatedsuch that the second pseudorandom number sequence is synchronized withthe sequence of random numbers generated at the first wireless device.8. The method of claim 1, wherein the transmitted signal configured tofacilitate position determination at the second wireless device isconfigured to facilitate position determination at the second wirelessdevice based on one or more of: a received signal strength indicator(RSSI)-based positioning determination process, a round trip time(RTT)-based position determination process, a speed-based positiondetermination process aided by an inertial navigation system, or anycombination thereof.
 9. The method of claim 8, wherein the RSSI-basedposition determination process comprises an RSSI-fingerprinting process,and the RTT-based position determination process comprises anRTT-fingerprinting process.
 10. The method of claim 1, wherein the firstwireless device comprises an access point.
 11. The method of claim 10,wherein the access point comprises a WiFi-based station.
 12. The methodof claim 1, wherein the second wireless device comprises a preauthorizedwireless device equipped with an undithering unit configured to enableundithering of the signal with the at least one PHY-layer signalparameter value controllably modified at the first wireless deviceaccording to the at least one pre-determined varying signal modificationprocess.
 13. A wireless device comprising: one or more processors; andstorage media comprising computer instructions that, when executed onthe one or more processors, cause operations comprising: controllablymodifying an original unmodified value of at least one PHY-layer signalparameter for a signal according to at least one pre-determined varyingsignal modification process, the at least one PHY-layer signal parametercomprising: amplitude, frequency, timestamp, gain, signal equalization,or any combination thereof; and transmitting, to an other wirelessdevice, the signal with a controllably modified value of the at leastone PHY-layer signal parameter, the transmitted signal configured tofacilitate position determination of the other wireless device when theoriginal unmodified value of the at least one PHY-layer signal parameteris determined at the other wireless device from the controllablymodified value of the at least one PHY-layer signal parameter.
 14. Thewireless device of claim 13, wherein controllably modifying the originalunmodified value of the at least one PHY-layer signal parameteraccording to the at least one pre-determined varying signal modificationprocess comprises: controllably modifying original unmodified values oftwo or more PHY-layer signal parameters according to respectivedifferent pre-determined varying signal modification processes.
 15. Thewireless device of claim 14, wherein one of the two or more PHY-layersignal parameters comprises at least one of: delay or phase.
 16. Thewireless device of claim 13, wherein controllably modifying the originalunmodified value of the at least one PHY-layer signal parameteraccording to the at least one pre-determined varying signal modificationprocess comprises: controllably modifying the original unmodified valueof the at least one PHY-layer signal parameter according to apseudorandom-time-variation-based process.
 17. The wireless device ofclaim 13, wherein controllably modifying the original unmodified valueof the at least one PHY-layer signal parameter according to the at leastone pre-determined varying signal modification process comprises:controllably modifying the original unmodified value of the at least onePHY-layer signal parameter according to an autoregressive moving averageprocess.
 18. The wireless device of claim 17, wherein controllablymodifying the original unmodified value of the at least one PHY-layersignal parameter according to the autoregressive moving average processcomprises: generating a sequence of random numbers based on apseudorandom generator process; inputting the sequence of random numbersto a z-transform implementation of the autoregressive moving averageprocess to generate a resultant sequence; and modifying the originalunmodified value of the at least one PHY-layer signal parameter based onthe resultant sequence.
 19. The wireless device of claim 13, wherein thetransmitted signal configured to facilitate position determination atthe other wireless device is configured to facilitate positiondetermination at the other wireless device based on one or more of: areceived signal strength indicator (RSSI)-based positioningdetermination process, a round trip time (RTT)-based positiondetermination process, a speed-based position determination processaided by an inertial navigation system, or any combination thereof. 20.An apparatus comprising: means for controllably modifying an originalunmodified value of at least one PHY-layer signal parameter for a signalaccording to at least one pre-determined varying signal modificationprocess, the at least one PHY-layer signal parameter comprising:amplitude, frequency, timestamp, gain, signal equalization, or anycombination thereof; and means for transmitting, to a receiving wirelessdevice, the signal with a controllably modified value of the at leastone PHY-layer signal parameter, the transmitted signal configured tofacilitate position determination of the receiving wireless device whenthe original unmodified value of the at least one PHY-layer signalparameter is determined at the receiving wireless device from thecontrollably modified value of the at least one PHY-layer signalparameter.
 21. The apparatus of claim 20, wherein the means forcontrollably modifying the original unmodified value of the at least onePHY-layer signal parameter according to the at least one pre-determinedvarying signal modification process comprises: means for controllablymodifying original unmodified values of two or more PHY-layer signalparameters according to respective different pre-determined varyingsignal modification processes.
 22. The apparatus of claim 21, whereinone of the two or more PHY-layer signal parameters comprises at leastone of: delay or phase.
 23. The apparatus of claim 20, wherein the meansfor controllably modifying the original unmodified value of the at leastone PHY-layer signal parameter according to the at least onepre-determined varying signal modification process comprises: means forcontrollably modifying the original unmodified value of the at least onePHY-layer signal parameter according to apseudorandom-time-variation-based process.
 24. The apparatus of claim20, wherein the means for controllably modifying the original unmodifiedvalue of the at least one PHY-layer signal parameter according to the atleast one pre-determined varying signal modification process comprises:means for controllably modifying the original unmodified value of the atleast one PHY-layer signal parameter according to an autoregressivemoving average process.
 25. The apparatus of claim 24, wherein the meansfor controllably modifying the original unmodified value of the at leastone PHY-layer signal parameter according to the autoregressive movingaverage process comprises: means for generating a sequence of randomnumbers based on a pseudorandom generator process; means for inputtingthe sequence of random numbers to a z-transform implementation of theautoregressive moving average process to generate a resultant sequence;and means for modifying the original unmodified value of the at leastone PHY-layer signal parameter based on the resultant sequence.
 26. Theapparatus of claim 20, wherein the transmitted signal configured tofacilitate position determination at the receiving wireless device isconfigured to facilitate position determination at the receivingwireless device based on one or more of: a received signal strengthindicator (RSSI)-based positioning determination process, a round triptime (RTT)-based position determination process, a speed-based positiondetermination process aided by an inertial navigation system, or anycombination thereof.
 27. A processor readable media programmed with aset of instructions executable on a processor that, when executed,causes operations comprising: controllably modifying, at a firstwireless device, an original unmodified value of at least one PHY-layersignal parameter for a signal according to at least one pre-determinedvarying signal modification process, the at least one PHY-layer signalparameter comprising: amplitude, frequency, timestamp, gain, signalequalization, or any combination thereof; and transmitting, to a secondwireless device, the signal with a controllably modified value of the atleast one PHY-layer signal parameter, the transmitted signal configuredto facilitate position determination of the second wireless device whenthe original unmodified value of the at least one PHY-layer signalparameter is determined at the second wireless device from thecontrollably modified value of the at least one PHY-layer signalparameter.
 28. The processor readable media of claim 27, whereincontrollably modifying the original unmodified value of the at least onePHY-layer signal parameter according to the at least one pre-determinedvarying signal modification process comprises: controllably modifyingoriginal unmodified values of two or more PHY-layer signal parametersaccording to respective different pre-determined varying signalmodification processes.
 29. The processor readable media of claim 28,wherein one of the two or more PHY-layer signal parameters comprises atleast one of: delay or phase.
 30. The processor readable media of claim27, wherein controllably modifying the original unmodified value of theat least one PHY-layer signal parameter according to the at least onepre-determined varying signal modification process comprises:controllably modifying the original unmodified value of the at least onePHY-layer signal parameter according to apseudorandom-time-variation-based process.
 31. The processor readablemedia of claim 27, wherein controllably modifying the originalunmodified value of the at least one PHY-layer signal parameteraccording to the at least one pre-determined varying signal modificationprocess comprises: controllably modifying the original unmodified valueof the at least one PHY-layer signal parameter according to anautoregressive moving average process.
 32. The processor readable mediaof claim 31, wherein controllably modifying the original unmodifiedvalue of the at least one PHY-layer signal parameter according to theautoregressive moving average process comprises: generating a sequenceof random numbers based on a pseudorandom generator process; inputtingthe sequence of random numbers to a z-transform implementation of theautoregressive moving average process to generate a resultant sequence;and modifying the original unmodified value of the at least onePHY-layer signal parameter based on the resultant sequence.
 33. Theprocessor readable media of claim 27, wherein the transmitted signalconfigured to facilitate position determination at the second wirelessdevice is configured to facilitate position determination at the secondwireless device based on one or more of: a received signal strengthindicator (RSSI)-based positioning determination process, a round triptime (RTT)-based position determination process, a speed-based positiondetermination process aided by an inertial navigation system, or anycombination thereof.
 34. A method comprising: receiving at a firstwireless device a signal, transmitted from a second wireless device,with a controllably modified at least one PHY-layer signal parametervalue that was generated according to at least one pre-determinedvarying signal modification process applied to an original unmodifiedvalue of at least one PHY-layer signal parameter, the at least onePHY-layer signal parameter comprising: amplitude, frequency, timestamp,gain, signal equalization, or any combination thereof; determining, fromthe received signal, the original unmodified value of the at least onePHY-layer signal parameter; and determining a position of the firstwireless device based, at least in part, on the original unmodifiedvalue of the at least one PHY-layer signal parameter of the signal,determined from the controllably modified at least one PHY-layer signalparameter value of the signal received at the first wireless device. 35.The method of claim 34, wherein the controllably modified at least onePHY-layer signal parameter value of the received signal generatedaccording to the at least one pre-determined varying signal modificationprocess comprises: controllably modified two or more PHY-layer signalparameter values generated according to respective differentpre-determined varying signal modification processes applied torespective original unmodified values of two or more PHY-layer signalparameters of the signal transmitted from the second wireless device.36. The method of claim 35, wherein one of the two or more PHY-layersignal parameters comprises at least one of: delay or phase.
 37. Themethod of claim 34, wherein the controllably modified at least onePHY-layer signal parameter value of the received signal generatedaccording to the at least one pre-determined varying signal modificationprocess is generated according to a pseudorandom-time-variation-basedprocess applied to the original unmodified value of the at least onePHY-layer signal parameter of the signal transmitted from the secondwireless device.
 38. The method of claim 34, wherein the controllablymodified at least one PHY-layer signal parameter value of the receivedsignal generated according to the at least one pre-determined varyingsignal modification process is generated according to an autoregressivemoving average process applied to the original unmodified value of theat least one PHY-layer signal parameter of the signal transmitted fromthe second wireless device.
 39. The method of claim 38, wherein thecontrollably modified at least one PHY-layer signal parameter valuegenerated according to the autoregressive moving average process isgenerated by: generating, at the second wireless device, a sequence ofrandom numbers based on a pseudorandom generator process; inputting, atthe second wireless device, the sequence of random numbers to az-transform implementation of the autoregressive moving average processto generate a resultant sequence; and modifying, at the second wirelessdevice, the original unmodified value of the at least one PHY-layersignal parameter based on the resultant sequence.
 40. The method ofclaim 39, further comprising: synchronizing a first clock at the firstwireless device to a second clock at the second wireless device relativeto a reference time; and generating a second pseudorandom numbersequence at the first wireless device such that the second pseudorandomnumber sequence is synchronized with the sequence of random numbersgenerated at the second wireless device.
 41. The method of claim 34,wherein determining the position of the first wireless device comprises:determining the position of the first wireless device based on one ormore of: a received signal strength indicator (RSSI)-based positioningdetermination process, a round trip time (RTT)-based positiondetermination process, a speed-based position determination processaided by an inertial navigation system, or any combination thereof. 42.The method of claim 41, wherein the RSSI-based position determinationprocess comprises an RSSI-fingerprinting process, and the RTT-basedposition determination process comprises an RTT-fingerprinting process.43. The method of claim 34, wherein the second wireless device comprisesan access point.
 44. The method of claim 34, wherein the first wirelessdevice comprises a preauthorized wireless device equipped with anundithering unit configured to enable undithering of the signal with theat least one PHY-layer signal parameter value controllably modified atthe second wireless device according to the at least one pre-determinedvarying signal modification process.
 45. A wireless device comprising:one or more processors; and storage media comprising computerinstructions that, when executed on the one or more processors, causeoperations comprising: receiving a signal, transmitted from an otherwireless device, with a controllably modified at least one PHY-layersignal parameter value that was generated according to at least onepre-determined varying signal modification process applied to anoriginal unmodified value of at least one PHY-layer signal parameter,the at least one PHY-layer signal parameter comprising one or more of:amplitude, frequency, timestamp, gain, signal equalization, or anycombination thereof; determining, from the received signal, the originalunmodified value of the at least one PHY-layer signal parameter; anddetermining a position of the wireless device based, at least in part,on the original unmodified value of the at least one PHY-layer signalparameter of the signal, determined from the at least one PHY-layersignal parameter value of the signal received at the wireless device.46. The wireless device of claim 45, wherein the controllably modifiedat least one PHY-layer signal parameter value of the received signalgenerated according to the at least one pre-determined varying signalmodification process comprises: controllably modified two or morePHY-layer signal parameter values generated according to respectivedifferent pre-determined varying signal modification processes appliedto respective original unmodified values of two or more PHY-layer signalparameters of the signal transmitted from the other wireless device. 47.The wireless device of claim 46, wherein one of the two or morePHY-layer signal parameters comprises at least one of: delay or phase.48. The wireless device of claim 45, wherein the controllably modifiedat least one PHY-layer signal parameter value of the received signalgenerated according to the at least one pre-determined varying signalmodification process is generated according to apseudorandom-time-variation-based process applied to the originalunmodified value of the at least one PHY-layer signal parameter of thesignal transmitted from the other wireless device.
 49. The wirelessdevice of claim 45, wherein the controllably modified at least onePHY-layer signal parameter value of the received signal generatedaccording to the at least one pre-determined varying signal modificationprocess is generated according to an autoregressive moving averageprocess applied to the original unmodified value of the at least onePHY-layer signal parameter of the signal transmitted from the otherwireless device.
 50. The wireless device of claim 49, wherein thecontrollably modified at least one PHY-layer signal parameter valuegenerated according to the autoregressive moving average process isgenerated by: generating, at the other wireless device, a sequence ofrandom numbers based on a pseudorandom generator process; inputting, atthe other wireless device, the sequence of random numbers to az-transform implementation of the autoregressive moving average processto generate a resultant sequence; and modifying, at the other wirelessdevice, the original unmodified value of the at least one PHY-layersignal parameter based on the resultant sequence.
 51. The wirelessdevice of claim 50, wherein the storage media comprises furtherinstructions that, when executed, cause further operations comprising:synchronizing a clock at the wireless device to an other clock at theother wireless device relative to a reference time; and generating asecond pseudorandom number sequence at the wireless device such that thesecond pseudorandom number sequence is synchronized with the sequence ofrandom numbers generated at the other wireless device.
 52. The wirelessdevice of claim 45, wherein determining the position of the wirelessdevice comprises: determining the position of the wireless device basedon one or more of: a received signal strength indicator (RSSI)-basedpositioning determination process, a round trip time (RTT)-basedposition determination process, a speed-based position determinationprocess aided by an inertial navigation system, or any combinationthereof.
 53. An apparatus comprising: means for receiving a signal,transmitted from a transmitting wireless device, with a controllablymodified at least one PHY-layer signal parameter value that wasgenerated according to at least one pre-determined varying signalmodification process applied to an original unmodified value of at leastone PHY-layer signal parameter, the at least one PHY-layer signalparameter comprising one or more of: amplitude, frequency, timestamp,gain, signal equalization, or any combination thereof; means fordetermining, from the received signal, the original unmodified value ofthe at least one PHY-layer signal parameter; and means for determining aposition of the apparatus based, at least in part, on the originalunmodified value of the at least one PHY-layer signal parameter of thesignal, determined from the controllably modified at least one PHY-layersignal parameter value of the signal received at the apparatus.
 54. Theapparatus of claim 53, wherein the controllably modified at least onePHY-layer signal parameter value of the received signal generatedaccording to the at least one pre-determined varying signal modificationprocess comprises: controllably modified two or more PHY-layer signalparameter values generated according to respective differentpre-determined varying signal modification processes applied torespective original unmodified values of two or more PHY-layer signalparameters of the signal transmitted from the transmitting wirelessdevice.
 55. The apparatus of claim 54, wherein one of the two or morePHY-layer signal parameters comprises at least one of: delay or phase.56. The apparatus of claim 53, wherein the controllably modified atleast one PHY-layer signal parameter value of the received signalgenerated according to the at least one pre-determined varying signalmodification process is generated according to apseudorandom-time-variation-based process applied to the originalunmodified value of the at least one PHY-layer signal parameter of thesignal transmitted from the transmitting wireless device.
 57. Theapparatus of claim 53, wherein the controllably modified at least onePHY-layer signal parameter value of the received signal generatedaccording to the at least one pre-determined varying signal modificationprocess is generated according to an autoregressive moving averageprocess applied to the original unmodified value of the at least onePHY-layer signal parameter of the signal transmitted from thetransmitting wireless device.
 58. The apparatus of claim 57, wherein thecontrollably modified at least one PHY-layer signal parameter valuegenerated according to the autoregressive moving average process isgenerated by: generating, at the transmitting wireless device, asequence of random numbers based on a pseudorandom generator process;inputting, at the transmitting wireless device, the sequence of randomnumbers to a z-transform implementation of the autoregressive movingaverage process to generate a resultant sequence; and modifying, at thetransmitting wireless device, the original unmodified value of the atleast one PHY-layer signal parameter based on the resultant sequence.59. The apparatus of claim 58, further comprising: means forsynchronizing a clock at the apparatus to an other clock at thetransmitting wireless device relative to a reference time; and means forgenerating a second pseudorandom number sequence at the apparatus suchthat the second pseudorandom number sequence is synchronized with thesequence of random numbers generated at the transmitting wirelessdevice.
 60. The apparatus of claim 53, wherein the means for determiningthe position of the apparatus comprises: means for determining theposition of the apparatus based on one or more of: a received signalstrength indicator (RSSI)-based positioning determination process, around trip time (RTT)-based position determination process, aspeed-based position determination process aided by an inertialnavigation system, or any combination thereof.
 61. A processor readablemedia programmed with a set of instructions executable on a processorthat, when executed, causes operations comprising: receiving at a firstwireless device a signal, transmitted from a second wireless device,with a controllably modified at least one PHY-layer signal parametervalue that was generated according to at least one pre-determinedvarying signal modification process applied to an original unmodifiedvalue of at least one PHY-layer signal parameter, the controllablymodified at least one PHY-layer signal parameter comprising: amplitude,frequency, phase, delay, timestamp, gain, signal equalization, or anycombination thereof; determining, from the received signal, the originalunmodified value of the at least one PHY-layer signal parameter value;and determining a position of the first wireless device based, at leastin part, on the original unmodified value of the at least one PHY-layersignal parameter of the signal, determined from the controllablymodified at least one PHY-layer signal parameter value of the signalreceived at the first wireless device.
 62. The processor readable mediaof claim 61, wherein the controllably modified at least one PHY-layersignal parameter value of the received signal generated according to theat least one pre-determined varying signal modification processcomprises: controllably modified two or more PHY-layer signal parametervalues generated according to respective different pre-determinedvarying signal modification processes applied to respective originalunmodified values of two or more PHY-layer signal parameters of thesignal transmitted from the second wireless device.
 63. The processorreadable media of claim 62, wherein one of the two or more PHY-layersignal parameters comprises at least one of: delay or phase.
 64. Theprocessor readable media of claim 61, wherein the controllably modifiedat least one PHY-layer signal parameter value of the received signalgenerated according to the at least one pre-determined varying signalmodification process is generated according to apseudorandom-time-variation-based process applied to the originalunmodified value of the at least one PHY-layer signal parameter of thesignal transmitted from the second wireless device.
 65. The processorreadable media of claim 61, wherein the controllably modified at leastone PHY-layer signal parameter value of the received signal generatedaccording to the at least one pre-determined varying signal modificationprocess is generated according to an autoregressive moving averageprocess applied to the original unmodified value of the controllablymodified at least one PHY-layer signal parameter of the signaltransmitted from the second wireless device.
 66. The processor readablemedia of claim 65, wherein the controllably modified at least onePHY-layer signal parameter value generated according to theautoregressive moving average process is generated by: generating, atthe second wireless device, a sequence of random numbers based on apseudorandom generator process; inputting, at the second wirelessdevice, the sequence of random numbers to a z-transform implementationof the autoregressive moving average process to generate a resultantsequence; and modifying, at the second wireless device, the originalunmodified value of the at least one PHY-layer signal parameter based onthe resultant sequence.
 67. The processor readable media of claim 66,further comprising instructions that, when executed, cause furtheroperations comprising: synchronizing a first clock at the first wirelessdevice to a second clock at the second wireless device relative to areference time; and generating a second pseudorandom number sequence atthe first wireless device such that the second pseudorandom numbersequence is synchronized with the sequence of random numbers generatedat the second wireless device.
 68. The processor readable media of claim62, wherein determining the position of the first wireless devicecomprises: determining the position of the first wireless device basedon one or more of: a received signal strength indicator (RSSI)-basedpositioning determination process, a round trip time (RTT)-basedposition determination process, a speed-based position determinationprocess aided by an inertial navigation system, or any combinationthereof.